[gtk] window: Don't try to size-allocate unmapped popovers

[Timm Bäder <baedert src gnome org>]

commit fb6adaaa622f8fac2d937a09c992973f94f5afff
Author: Timm Bäder <mail baedert org>
Date:   Sun Dec 2 12:58:07 2018 +0100

    window: Don't try to size-allocate unmapped popovers
    
    The gtk_widget_size_allocate call won't do anything anyway.

 gtk/gtkwindow.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index f1e99e5792..339b0e6f89 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -7111,6 +7111,9 @@ popover_size_allocate (GtkWindowPopover *popover,
 {
   cairo_rectangle_int_t rect;
 
+  if (!gtk_widget_get_mapped (popover->widget))
+    return;
+
   if (GTK_IS_POPOVER (popover->widget))
     gtk_popover_update_position (GTK_POPOVER (popover->widget));