Fix exception in Frontend\Core\Engine\Theme::getPath.

found an exception once added the tag cloud widget to a page:
```
Message 	The template (/home/jezek/public_html/www/app/../src/Frontend/Modules/Tags/Layout/Widgets/TagCloud.tpl) does not exists.
File 	/home/jezek/public_html/www/src/Frontend/Core/Engine/Theme.php
Line 	57
```
This fixes it ;)