[gnome-calculator] Fixes a crash in gnome-calculator when calculating nested pows.

[Arth Patel <arthpatel src gnome org>]

commit 4a0e2c068dfaa7c0752b7fbf171b620c34a433bd
Author: Santiago Saavedra <santiagosaavedra gmail com>
Date:   Mon Apr 15 22:56:31 2013 +0200

    Fixes a crash in gnome-calculator when calculating nested pows.
    
    Example test case:
      Input: 2³ ²
      Outcome: segfault
      Expected output: 512 (consistent with 2^3^2)
    
    Checking against right.token in the calculatin allows us to know whether
    we are in a nested calculation and should avoid atoi (as it should have
    already been done) or not.

 src/equation-parser.vala |   18 +++++++++++++++++-
 1 files changed, 17 insertions(+), 1 deletions(-)
---
diff --git a/src/equation-parser.vala b/src/equation-parser.vala
index d3cf977..acbdd9d 100644
--- a/src/equation-parser.vala
+++ b/src/equation-parser.vala
@@ -509,6 +509,9 @@ public class XPowYNode : LRNode
     }
 }
 
+/**
+ * This class is a XPowY in which the right token is an nsup number.
+ */
 public class XPowYIntegerNode : ParseNode
 {
     public XPowYIntegerNode (Parser parser, LexerToken? token, uint precedence, Associativity associativity)
@@ -519,7 +522,20 @@ public class XPowYIntegerNode : ParseNode
     public override Number? solve ()
     {
         var val = left.solve ();
-        var pow = super_atoi (right.token.text);
+
+        // Are we inside a nested pow?
+        if (val == null)
+        {
+            val = new Number.integer (super_atoi (left.token.text));
+        }
+
+        int64 pow;
+
+        if (right.token != null)
+            pow = super_atoi (right.token.text);
+        else
+            pow = right.solve ().to_integer ();
+
         if (val == null)
             return null;