Avoid an infinite loop which could jam ProxyService

If an operation with an empty dictionary of entities to create/update
was added to the queue, data[i] could become empty with task_count[i]
still being positive. Therefore no data would have ever been sent (and
thus task_count would have never been reset to zero) but the loop would
also have never yielded to other greenlets, making ProxyService stuck
(and taking up 100% of the CPU).

cms/service/ProxyService.py

@@ -198,7 +198,7 @@ def run(self):
             try:
                 for i in xrange(self.TYPE_COUNT):
                     # Send entities of type i.
-                    if len(data[i]) > 0:
+                    if task_count[i] > 0:
                         # XXX We abuse the resource path as the english
                         # (plural) name for the entity type.
                         name = self.RESOURCE_PATHS[i]