[gtk/wip/albfan/protect-begin_move_drag] Define begin_move_drag

[Alberto Fanjul <albfan src gnome org>]

commit 46b92412a7bcd9d14fe21abbb9bd923d4dd50656
Author: Alberto Fanjul <albfan gnome org>
Date:   Sat Mar 21 10:03:10 2020 +0100

    Define begin_move_drag
    
    Avoid crashes calling it on drag and drop gestures
    
    fixes #2532

 gdk/gdkoffscreenwindow.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
---
diff --git a/gdk/gdkoffscreenwindow.c b/gdk/gdkoffscreenwindow.c
index 2caf0affe0..710bd94d7c 100644
--- a/gdk/gdkoffscreenwindow.c
+++ b/gdk/gdkoffscreenwindow.c
@@ -644,6 +644,15 @@ gdk_offscreen_window_set_wmfunctions (GdkWindow        *window,
 {
 }
 
+static void
+gdk_offscreen_window_begin_move_drag (GdkWindow *window,
+                                      gint       button,
+                                      gint       root_x,
+                                      gint       root_y,
+                                      guint32    timestamp)
+{
+}
+
 static void
 gdk_offscreen_window_set_transient_for (GdkWindow *window,
                                        GdkWindow *another)
@@ -754,7 +763,7 @@ gdk_offscreen_window_class_init (GdkOffscreenWindowClass *klass)
   impl_class->get_decorations = NULL;
   impl_class->set_functions = gdk_offscreen_window_set_wmfunctions;
   impl_class->begin_resize_drag = NULL;
-  impl_class->begin_move_drag = NULL;
+  impl_class->begin_move_drag = gdk_offscreen_window_begin_move_drag;
   impl_class->enable_synchronized_configure = gdk_offscreen_window_do_nothing;
   impl_class->configure_finished = NULL;
   impl_class->set_opacity = gdk_offscreen_window_set_opacity;