stagger: hide element in Enable.

This should fix the issue pointed out by Rainrider, see https://github.com/haste/oUF/commit/ac2fb02e3a572c2fd53ddefd17f77021127c2e1a#commitcomment-4974904.
Merge pull request #213 from Adirelle/stagger-fix

stagger: hide element in Enable.