Textfield Value Should Be fails with NPE on input type=url

[php-coder]

The keyword Textfield Value Should Be fails with NullPointerException, when it's used for getting a value from the <input type=url>:

java.lang.RuntimeException
	at org.robotframework.javalib.library.AnnotationLibrary.retrieveInnerException(AnnotationLibrary.java:148)
	at org.robotframework.javalib.library.AnnotationLibrary.runKeyword(AnnotationLibrary.java:130)
	at com.github.markusbernhardt.selenium2library.Selenium2Library.runKeyword(Selenium2Library.java:499)
	at robot.model.testcase$py.visit$7(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testcase.py:74)
	at robot.model.testcase$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testcase.py)
	at robot.model.itemlist$py.visit$11(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/itemlist.py:75)
	at robot.model.itemlist$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/itemlist.py)
	at robot.model.visitor$py.visit_suite$2(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/visitor.py:88)
	at robot.model.visitor$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/visitor.py)
	at robot.model.testsuite$py.visit$19(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testsuite.py:161)
	at robot.model.testsuite$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testsuite.py)
	at robot.model.itemlist$py.visit$11(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/itemlist.py:75)
	at robot.model.itemlist$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/itemlist.py)
	at robot.model.visitor$py.visit_suite$2(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/visitor.py:88)
	at robot.model.visitor$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/visitor.py)
	at robot.model.testsuite$py.visit$19(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testsuite.py:161)
	at robot.model.testsuite$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testsuite.py)
	at robot.model.itemlist$py.visit$11(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/itemlist.py:75)
	at robot.model.itemlist$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/itemlist.py)
	at robot.model.visitor$py.visit_suite$2(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/visitor.py:88)
	at robot.model.visitor$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/visitor.py)
	at robot.model.testsuite$py.visit$19(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testsuite.py:161)
	at robot.model.testsuite$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testsuite.py)
	at robot.model.itemlist$py.visit$11(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/itemlist.py:75)
	at robot.model.itemlist$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/itemlist.py)
	at robot.model.visitor$py.visit_suite$2(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/visitor.py:88)
	at robot.model.visitor$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/visitor.py)
	at robot.model.testsuite$py.visit$19(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testsuite.py:161)
	at robot.model.testsuite$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/model/testsuite.py)
	at robot.run$py.main$3(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/run.py:452)
	at robot.run$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/run.py)
	at robot.utils.application$py._execute$10(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/utils/application.py:94)
	at robot.utils.application$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/utils/application.py)
	at robot.utils.application$py.execute_cli$5(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/utils/application.py:49)
	at robot.utils.application$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/utils/application.py)
	at robot.run$py.run_cli$7(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/run.py:489)
	at robot.run$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/run.py)
	at robot.jarrunner$py._run$3(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/jarrunner.py:64)
	at robot.jarrunner$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/jarrunner.py)
	at robot.jarrunner$py.run$2(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/jarrunner.py:57)
	at robot.jarrunner$py.call_function(/Users/jmalinen/Documents/workspace/robotframework/build/Lib/robot/jarrunner.py)
	at org.robotframework.RobotRunner.run(RobotRunner.java:74)
	at org.robotframework.RobotFramework.run(RobotFramework.java:61)
	at org.robotframework.mavenplugin.AcceptanceTestMojo.executeRobot(AcceptanceTestMojo.java:73)
	at org.robotframework.mavenplugin.AcceptanceTestMojo.subclassExecute(AcceptanceTestMojo.java:68)
	at org.robotframework.mavenplugin.AbstractMojoWithLoadedClasspath.execute(AbstractMojoWithLoadedClasspath.java:53)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: java.lang.NullPointerException
	at com.github.markusbernhardt.selenium2library.keywords.FormElement.textfieldValueShouldBe(FormElement.java:504)
	at com.github.markusbernhardt.selenium2library.keywords.FormElement.textfieldValueShouldBe(FormElement.java:479)
	at org.robotframework.javalib.reflection.KeywordInvoker.invoke(KeywordInvoker.java:50)
	at org.robotframework.javalib.beans.annotation.AnnotationKeywordExtractor$1.execute(AnnotationKeywordExtractor.java:62)
	at org.robotframework.javalib.beans.annotation.AnnotationKeywordExtractor$2.execute(AnnotationKeywordExtractor.java:86)
	at org.robotframework.javalib.library.KeywordFactoryBasedLibrary.runKeyword(KeywordFactoryBasedLibrary.java:37)
	at org.robotframework.javalib.library.AnnotationLibrary.runKeyword(AnnotationLibrary.java:128)
	... 226 more