boxPointer: Fix arrow's position the second time a folder is opened
(This is a downstream fix from Endless, but the issue happens upstream too)
The second time a folder is opened, the arrow of the folder popup will be shown in the wrong position (as if pushed to the left). This is due to its transformed position, which is affected depending on the allocation of the boxPointer's container.
This patch simply queues a repaint when the allocation is changed which fixes the issue.