Try/except around outbound stanza processing

to avoid killing the send loop when a filter has an error

slixmpp/xmlstream/xmlstream.py

@@ -902,6 +902,7 @@ class XMLStream(asyncio.BaseProtocol):
         """
         while True:
             (data, use_filters) = await self.waiting_queue.get()
+            try:
                 if isinstance(data, ElementBase):
                     if use_filters:
                         for filter in self.__filters['out']:
@@ -926,6 +927,8 @@ class XMLStream(asyncio.BaseProtocol):
                     self.send_raw(str_data)
                 else:
                     self.send_raw(data)
+            except:
+                log.error('Could not send stanza %s', data, exc_info=True)
             self.waiting_queue.task_done()
 
     def send(self, data, use_filters=True):