Two crash fixes; regression fix; increase max FPS

Whilst debugging, I suddenly got a crash from Error::run which was caused by mem_del called by Blob::~Blob.
1. Fixes the error (occurs when using the Mem class) in Blob. *
2. Fixes an error in Error::run, which caused deinit functions to cause Access Violations.
3. Fixes a regression introduced by [44cc7c71041 Main menu's exit](http://7kfans.com/git/?p=7kaa.git;a=commit;h=44cc7c71041c93f8b8e604fab0b0a2fb0457f0b2), where the ingame Load menu would not open any more.
4. Changes the FPS to just under 59 fps maximum. Related to [c668f4c7aa VgaSDL: ...](http://7kfans.com/git/?p=7kaa.git;a=commit;h=c668f4c7aa49cb69e1e04d06a62fe1e39175307e)


\* Should we perhaps define NO_MEM_CLASS when building release?