diff -r 151e73a02caf -r 56c4fe6b7012 Viewer.py
--- a/Viewer.py	Wed Nov 26 09:07:27 2008 +0100
+++ b/Viewer.py	Wed Nov 26 09:08:04 2008 +0100
@@ -895,8 +895,10 @@
                     connectors["outputs"].append((output["name"], None, output["edge"]))
                 else:
                     connectors["outputs"].append((output["name"], None, "none"))
-            if connectors["inputs"][0][0] == "EN" and connectors["outputs"][0][0] == "ENO":
-                connectors["inputs"].pop(0)
+            if len(connectors["inputs"]) > 0 and connectors["inputs"][0][0] == "EN":
+		connectors["inputs"].pop(0)
+	        executionControl = True
+            if len(connectors["outputs"]) > 0 and connectors["outputs"][0][0] == "ENO":
                 connectors["outputs"].pop(0)
                 executionControl = True
             if instance["name"] is None: