[gtk/matthiasc/for-master] picture: Don't leak alternative-test

[Matthias Clasen <matthiasc src gnome org>]

commit 3d008d592969363dbf9e131c4c3bd1becaef512c
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Jul 8 16:42:35 2020 -0400

    picture: Don't leak alternative-test
    
    This leak showed up while running the testsuite
    under asan.

 gtk/gtkpicture.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gtk/gtkpicture.c b/gtk/gtkpicture.c
index 0833b11a6f..31d814e381 100644
--- a/gtk/gtkpicture.c
+++ b/gtk/gtkpicture.c
@@ -284,6 +284,7 @@ gtk_picture_dispose (GObject *object)
   gtk_picture_set_paintable (self, NULL);
 
   g_clear_object (&self->file);
+  g_clear_pointer (&self->alternative_text, g_free);
 
   G_OBJECT_CLASS (gtk_picture_parent_class)->dispose (object);
 };