[core] Fix issue with !togglegm status not persisting correctly

[WinterSolstice8]

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What does this pull request do?

fixes #5636
Basically the code was just always turning on GM mode when you zoned because it was accessing the wrong variable (your gm mode, not what you set as visible gm)

Steps to test these changes

use !togglegm, with gm mode on when you zone, and see it persist.
use !togglegm, with gm mode off when you zone, and see gm mode not be on (instead of on all the time)