Ignore invoker events temporarily

This is a workaround for black palettes issue
reported in SL #2182.

Ignore the Invoker events right after the Palettes starts
opening or closening, at least for a litle while. In this
way we can prevent triggering the condition where Palettes
are turned emptry black.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Do not close Palette if ignoring events.

Let palettes to fully open before closing them.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>