fix for eebee9d

Author: heikoheiko

pyethereum/dispatch/dispatcher.py

@@ -161,7 +161,7 @@ def disconnect(self, receiver=None, sender=None, weak=True, dispatch_uid=None):
 
         with self.lock:
             self._clear_dead_receivers()
-            for index in self.receivers:
+            for index in range(len(self.receivers)):
                 (r_key, _) = self.receivers[index]
                 if r_key == lookup_key:
                     del self.receivers[index]