[Wiki] Internal Error on MediaWiki:Common.css

Somehow I broke MediaWiki:Common.css and now receive the following error on that page:
```
Internal error
[75a8bd5186b492deb3bd2773] 2019-05-01 15:42:23: Fatal exception of type "TypeError"
```

Will set these flags to show more debug output and track down the source of the issue:
```php
$wgShowExceptionDetails = true; $wgShowDBErrorBacktrace = true;
```