FIX making minify javascript fail-safe

This is an uncommon but pretty big issue. For example, if you have a bad javascript file, the minify process will throw an exception, which will be caught, then SS will attempt to show the error page, which will also use minified javascript, and fail the same way resulting in a blank page with nothing in the error logs.
You can `catch` an `ErrorException` here, as [PHPUnit converts warnings, etc to Exceptions](https://phpunit.de/manual/current/en/writing-tests-for-phpunit.html#writing-tests-for-phpunit.errors).