Added SeleniumLibraryNonFatalException to catch block in the CustomRobotDriverElement constr.

Author: YauheniPo

src/main/java/com/github/markusbernhardt/seleniumlibrary/CustomRobotDriverElement.java

@@ -22,7 +22,7 @@ public CustomRobotDriverElement() throws NoSuchFieldException, IllegalAccessExce
         try {
             CustomRobotDriverElement.s = getLibraryInstance();
         } catch (javax.script.ScriptException e) {
-            e.printStackTrace();
+            throw new SeleniumLibraryNonFatalException("Cannot create SeleniumLibrary instance: " + e.getMessage());
         }
         Field bmField = SeleniumLibrary.class.getDeclaredField("bm");
         bmField.setAccessible(true);