gfio: patch around widget destroy crash

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/gfio.c b/gfio.c
index 068f229..cbedaa2 100644
--- a/gfio.c
+++ b/gfio.c
@@ -1683,7 +1683,11 @@
 {
 	struct gui_entry *ge = data;
 
-	ge_destroy(ge);
+	/*
+	 * Why are we getting NULL data here sometimes?
+	 */
+	if (ge)
+		ge_destroy(ge);
 }
 
 static void gfio_quit(struct gui *ui)