world: always quit when quit is invoked
world: always quit when quit is invoked

Fix a thinko where World.quit(true) saves, but does not quit.

Possibly slightly over-engineered because I can't remember whether or
not foo = nil is syntactic sugar for "remove foo from lexical scope."

Signed-off-by: Gregory M. Turner <1f6d1f05bf03ff30afa6123e0bee2caa2da7cff0@be-evil.net>

Afforess/Factorio-Stdlib