**Setup**
* MediaWiki 1.27.0-rc.1 (5462877)
* PHP 5.6.22-0+deb8u1 (apache2handler)
* MariaDB 10.0.26-MariaDB-1~jessie
* MassEditRegex 8.1.0 (fa9f7d2)
**Issues**
This happens if I add an regex search for an non existing category, i.e. I tell the extension to work on category "xyz" and no category "xyz" exists.
```
2016-06-28 12:16:35 phalaris 0210020150926-02100_: [d8ebc15b03c698809a5c6cd6] /w/index.php?title=Sp%C3%A9cial:MassEditRegex&action=submit ErrorException from line 182 of /.../w/extensions/MassEditRegex/MassEditRegex.special.php: PHP Notice: Undefined variable: htmlDiff
#0 /.../w/extensions/MassEditRegex/MassEditRegex.special.php(182): MWExceptionHandler::handleError(integer, string, string, integer, array)
#1 /.../w/extensions/MassEditRegex/MassEditRegex.special.php(244): MassEditRegexSpecialPage->perform(boolean)
#2 /.../w/includes/specialpage/SpecialPage.php(479): MassEditRegexSpecialPage->execute(NULL)
#3 /.../w/includes/specialpage/SpecialPageFactory.php(576): SpecialPage->run(NULL)
#4 /.../w/includes/MediaWiki.php(282): SpecialPageFactory::executePath(Title, RequestContext)
#5 /.../w/includes/MediaWiki.php(745): MediaWiki->performRequest()
#6 /.../w/includes/MediaWiki.php(519): MediaWiki->main()
#7 /.../w/index.php(43): MediaWiki->run()
#8 {main}
```
Not sure how I got this:
```
Fatal error: Call to undefined method DifferenceEngine::setText() in /.../w/extensions/MassEditRegex/MassEditRegex.class.php on line 83
```