Fix most nullspace items, rewrite floor tiles not to del() on every place/remove
Typo fix
Bugfix.
Add defines, change comment
Fixes and guards against strange values
Merge pull request #7131 from GinjaNinja32/nullspace

Fixes most nullspace items, rewrites floor tiles not to del() so much
Merge pull request #7134 from Segrain/dev

Bugfix.