[gtk+] Never return NULL from gdk_get_program_class

[Timm Bäder <baedert src gnome org>]

commit a728a2e0612f234ba0cbaf17a2a36c9369b7754d
Author: Timm Bäder <mail baedert org>
Date:   Sun Feb 5 14:59:19 2017 +0100

    Never return NULL from gdk_get_program_class
    
    gdk_init is not calling g_set_prgname anymore, so just return a dummy
    string from gdk_get_program_class if it has not been set before.

 gdk/gdk.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/gdk/gdk.c b/gdk/gdk.c
index 423df80..c7cd32a 100644
--- a/gdk/gdk.c
+++ b/gdk/gdk.c
@@ -745,7 +745,10 @@ gdk_threads_add_timeout_seconds (guint       interval,
 const char *
 gdk_get_program_class (void)
 {
-  return gdk_progclass;
+  if (gdk_progclass)
+    return gdk_progclass;
+
+  return "GTK+ Application";
 }
 
 /**