[gimp] app: forgot precondition checks in gimpdisplayshell-grab.c

[Michael Natterer <mitch src gnome org>]

commit b338aa0e71b45d858aeb52d3528ed0c30ae88b1d
Author: Michael Natterer <mitch gimp org>
Date:   Sun Feb 20 13:16:46 2011 +0100

    app: forgot precondition checks in gimpdisplayshell-grab.c

 app/display/gimpdisplayshell-grab.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/app/display/gimpdisplayshell-grab.c b/app/display/gimpdisplayshell-grab.c
index 1320c0a..a9dc48f 100644
--- a/app/display/gimpdisplayshell-grab.c
+++ b/app/display/gimpdisplayshell-grab.c
@@ -59,6 +59,8 @@ void
 gimp_display_shell_pointer_ungrab (GimpDisplayShell *shell,
                                    GdkEvent         *event)
 {
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (event != NULL);
   g_return_if_fail (shell->pointer_grabbed == TRUE);
 
   gdk_display_pointer_ungrab (gtk_widget_get_display (shell->canvas),