Fixed bug introduced by preg_match change from php/php-src#1303

Fix from squizlabs/PHP_CodeSniffer@d397f87

Author: photodude

Joomla/Sniffs/Commenting/FileCommentSniff.php

@@ -530,15 +530,15 @@ protected function processCopyright(PHP_CodeSniffer_File $phpcsFile, array $tags
 			if (preg_match('/^.*?([0-9]{4})((.{1})([0-9]{4}))? (.+)$/', $content, $matches) !== 0)
 			{
 				// Check earliest-latest year order.
-				if ($matches[3] !== '')
+				if ($matches[3] !== '' && $matches[3] !== null)
 				{
 					if ($matches[3] !== '-')
 					{
 						$error = 'A hyphen must be used between the earliest and latest year';
 						$phpcsFile->addError($error, $tag, 'CopyrightHyphen');
 					}
 
-					if ($matches[4] !== '' && $matches[4] < $matches[1])
+					if ($matches[4] !== '' && $matches[4] !== null && $matches[4] < $matches[1])
 					{
 						$error = "Invalid year span \"$matches[1]$matches[3]$matches[4]\" found; consider \"$matches[4]-$matches[1]\" instead";
 						$phpcsFile->addWarning($error, $tag, 'InvalidCopyright');