Fix black palettes

Push the palette widget opening process to the latest
in order to avoid the race condition where the animation
takes of the place of the real palette.

Fixes #2184

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

src/sugar3/graphics/palette.py

@@ -211,8 +211,6 @@ class Palette(PaletteWindow):
         if self._invoker is not None:
             self._update_full_request()
 
-        PaletteWindow.popup(self, immediate)
-
         if state is None:
             state = self.PRIMARY
         self.set_palette_state(state)
@@ -222,6 +220,8 @@ class Palette(PaletteWindow):
         else:
             self._secondary_anim.stop()
 
+        PaletteWindow.popup(self, immediate)
+
     def popdown(self, immediate=False):
         if immediate:
             self._secondary_anim.stop()