I first wanted to write "but it's invalid ... and bad coding style". But then I educated myself and realised, it's actually completely valid and not that bad after all.
I think it's good to enforce semicolons in core DokuWiki nevertheless, just because it's our coding standard. But as the compressor is also for JS from plugins and templates, the authors of those definitely shouldn't be forced to use our coding standard. Therefore I think it's a good idea to improve our compressor so JS code works without optional semicolons.