[gtk+/gtk-3-16] Fix a cornercase crash

[Matthias Clasen <matthiasc src gnome org>]

commit bb0561f3561e45e39b81cbed1fdba6c48bf0b152
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu May 28 23:42:14 2015 -0400

    Fix a cornercase crash
    
    If gtk_text_layout_move_cursor_visually is called with a
    count of 0, we were passing NULL to a free function that
    can't handle it. Don't do that.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=750058

 gtk/gtktextlayout.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtktextlayout.c b/gtk/gtktextlayout.c
index 00dbefa..763ef3b 100644
--- a/gtk/gtktextlayout.c
+++ b/gtk/gtktextlayout.c
@@ -3660,7 +3660,8 @@ gtk_text_layout_move_iter_visually (GtkTextLayout *layout,
         gtk_text_iter_backward_char (iter);
     }
 
-  gtk_text_layout_free_line_display (layout, display);
+  if (display)
+    gtk_text_layout_free_line_display (layout, display);
 
  done: