Trigger rerender after masks set to panel buffer

This is especially important for the polar view. The panel buffer is
applied before warping, so masks being set to the polar view will
change the appearance of the polar view.

Signed-off-by: Patrick Avery <patrick.avery@kitware.com>

hexrdgui/masking/mask_manager.py

@@ -368,6 +368,8 @@ def masks_to_panel_buffer(self, selection):
                     mask = ~np.logical_or(~mask, ~buffer_value)
             buffer['value'] = mask
 
+        HexrdConfig().rerender_needed.emit()
+
     def clear_all(self):
         self.masks.clear()