Fixes an memory leak that occurs when no translation is found

If no translations was loaded then just delete the appTranslator object.
Simplify translate() code

Easier to read and understand.
Fixes another QTranslator related memory leak

Delete the QTranslator object if Qt translations aren't found. Warn also.
It's not very likely to happen, but it might happen.

I hate this brace coding style. So much wasted lines.