--- a/editors/TextViewer.py	Wed Dec 05 15:32:02 2012 +0100
+++ b/editors/TextViewer.py	Thu Dec 06 16:10:26 2012 +0100
@@ -694,7 +694,7 @@
                                             "extensible": False}
                         current_context = self.Variables
                     else:
-                        if char == '[':
+                        if char == '[' and current_context is not None:
                             self.ContextStack.append(current_context.get(word, None))
                         current_context = self.Variables