[gtk/gtk-3-24] wayland: Avoid crashes inside wl_proxy_marshal()

[Michael Catanzaro <mcatanzaro src gnome org>]

commit b4464e12742767a3dc08317371d665854286355f
Author: Michael Catanzaro <mcatanzaro posteo net>
Date:   Mon Sep 24 20:19:26 2018 +0000

    wayland: Avoid crashes inside wl_proxy_marshal()
    
    Suggested by Garnacho. Hopefully fixes #1349.
    
    Note: I'm riskily committing this via web UI not because I'm lazy
    (though I am :) but because I'm seeing a weird host key when I try to
    push or pull from GitLab.

 gdk/wayland/gdkwindow-wayland.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/gdk/wayland/gdkwindow-wayland.c b/gdk/wayland/gdkwindow-wayland.c
index 5f162770a0..a5f9d44912 100644
--- a/gdk/wayland/gdkwindow-wayland.c
+++ b/gdk/wayland/gdkwindow-wayland.c
@@ -932,6 +932,9 @@ gdk_window_impl_wayland_end_paint (GdkWindow *window)
   cairo_rectangle_int_t rect;
   int i, n;
 
+  if (!GDK_WINDOW_IS_MAPPED (window))
+    return;
+
   if (impl->staging_cairo_surface &&
       _gdk_wayland_is_shm_surface (impl->staging_cairo_surface) &&
       !window->current_paint.use_gl &&