From c1f236fce4e61e614862100ed7550796f86ce0bf Mon Sep 17 00:00:00 2001
From: Walter Bender <walter@sugarlabs.org>
Date: Wed, 18 Dec 2013 03:14:58 +0000
Subject: check for keys for backward compatibility

---
diff --git a/elements/elements.py b/elements/elements.py
index 4d9a361..625844c 100644
--- a/elements/elements.py
+++ b/elements/elements.py
@@ -595,7 +595,7 @@ class Elements:
         for (k,v) in worldmodel['additional_vars'].items():
             addvars[k] = v
 
-        if serialized:
+        if serialized and 'trackinfo' in addvars:
             trackinfo = addvars['trackinfo']
             for key, info in trackinfo.iteritems():
                 if not info[3]:
diff --git a/physics.py b/physics.py
index 6664f18..e89e12a 100644
--- a/physics.py
+++ b/physics.py
@@ -118,9 +118,11 @@ class PhysicsGame:
             path = self.opening_queue.encode('ascii', 'convert')
             if os.path.exists(path):
                 self.world.json_load(path, serialized=True)
-                self.full_pos_list = \
-                    self.world.additional_vars['full_pos_list']
-                self.trackinfo = self.world.additional_vars['trackinfo']
+                if 'full_pos_list' in self.world.additional_vars:
+                    self.full_pos_list = \
+                        self.world.additional_vars['full_pos_list']
+                if 'trackinfo' in self.world.additional_vars:
+                    self.trackinfo = self.world.additional_vars['trackinfo']
 
         while self.loop:
             while gtk.events_pending():
--
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