[gnome-calculator] math-equation: simplify some code

[Michael Catanzaro <mcatanzaro src gnome org>]

commit cf79ec3651ae2d757d3bf6bc08927fc96d899158
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Mon Dec 28 20:08:51 2015 -0600

    math-equation: simplify some code

 lib/math-equation.vala |    8 ++------
 1 files changed, 2 insertions(+), 6 deletions(-)
---
diff --git a/lib/math-equation.vala b/lib/math-equation.vala
index f982865..fa04177 100644
--- a/lib/math-equation.vala
+++ b/lib/math-equation.vala
@@ -510,13 +510,9 @@ public class MathEquation : Gtk.SourceBuffer
         undo_stack.remove (state);
         redo_stack.prepend (get_current_state ());
 
-        if (undo_stack == null)
-        {
-            apply_state (state);
-            return;
-        }
+        if (undo_stack != null)
+            state.ans = undo_stack.nth_data (0).ans;
 
-        state.ans = undo_stack.nth_data (0).ans;
         apply_state (state);
     }