[gnome-calculator/gnome-3-12] Restore ans to previous value when undo.

[Arth Patel <arthpatel src gnome org>]

commit 665ce4f7fa177ac2c0f046bdebd5eca353ea2c44
Author: Rodolphe PELLOUX-PRAYER <rodolphe damsy net>
Date:   Fri Jun 13 10:08:11 2014 +0200

    Restore ans to previous value when undo.

 src/math-equation.vala |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/math-equation.vala b/src/math-equation.vala
index 2afe358..160d923 100644
--- a/src/math-equation.vala
+++ b/src/math-equation.vala
@@ -487,6 +487,7 @@ public class MathEquation : Gtk.SourceBuffer
         status = ("");
         undo_stack.remove (state);
         redo_stack.prepend (get_current_state ());
+        state.ans = undo_stack.nth_data (0).ans;
 
         apply_state (state);
     }