This fixes the decoration rects for floating containers on a workspace
that is either tabbed or stacked. Without this, the floater would
incorrectly try to calculate where it's tab or stack decorations were
on the workspace. This would cause a SIGFPE (due to a divide-by-zero)
when the floater was on a tabbed workspace without any tiling children.
Furthermore, the floater does not care what the workspace's layout is
and should just use the location relative to the workspace. This should
have no effect on children of a floating container.
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