legacy bridge filtering code in bridgedb is suddenly hitting errors

18:11:46 DEBUG     L44:filters.bySubring()      Creating a filter for assigning bridges to subhashring 2-of-3...
18:11:46 DEBUG    L325:distributor.getBridges() Client request within time interval: 1526925600                                                                                             
18:11:46 DEBUG    L326:distributor.getBridges() Assigned client to subhashring 2/3
18:11:46 DEBUG    L327:distributor.getBridges() Assigned client to subhashring position: 726333b07ff8c62f7e44178f1b2153f28d953199                                    
18:11:46 DEBUG    L328:distributor.getBridges() Total bridges: 1540
18:11:46 DEBUG    L329:distributor.getBridges() Bridge filters: bySubring2of3 byIPv4()                                                                                          
18:11:46 DEBUG    L333:distributor.getBridges() Cache hit frozenset([<function bySubring2of3 at 0x7f267423dde8>, <function byIPv4() at 0x7f267727ce60>])
18:11:46 DEBUG    L269:distribute.bridgesPerR() Returning 3 bridges from ring of len: 508                    
18:11:46 DEBUG    L330:Bridges.getBridges()     Got duplicate bridge '72eaf88f51eaa96e2f4cab6fc360333b598ae19b' in main hashring for position '726333b07ff8c62f7e44178f1b2153f28d953199'.
18:11:46 DEBUG    L275:Bridges.filterDistinct() Got 7 possible bridges to filter
18:11:46 ERROR    L862:server.render()          'NoneType' object has no attribute 'version'      
Traceback (most recent call last):                                                                            
  File "/home/bridgedb/virtualenvs/bridgedb/local/lib/python2.7/site-packages/bridgedb-0.6.5+0.gd9741cf.dirty-py2.7.egg/bridgedb/distributors/https/server.py", line 860, in render
    response = self.getBridgeRequestAnswer(request)                                            
  File "/home/bridgedb/virtualenvs/bridgedb/local/lib/python2.7/site-packages/bridgedb-0.6.5+0.gd9741cf.dirty-py2.7.egg/bridgedb/distributors/https/server.py", line 904, in getBridgeRequestAnswer
    bridges = self.distributor.getBridges(bridgeRequest, interval)
  File "/home/bridgedb/virtualenvs/bridgedb/local/lib/python2.7/site-packages/bridgedb-0.6.5+0.gd9741cf.dirty-py2.7.egg/bridgedb/distributors/https/distributor.py", line 345, in getBridges
    answer = ring.getBridges(position, returnNum, filterBySubnet=True)                                  
  File "/home/bridgedb/virtualenvs/bridgedb/local/lib/python2.7/site-packages/bridgedb-0.6.5+0.gd9741cf.dirty-py2.7.egg/bridgedb/Bridges.py", line 334, in getBridges
    bridges = self.filterDistinctSubnets(keys)                                                                                                                                                                                      File "/home/bridgedb/virtualenvs/bridgedb/local/lib/python2.7/site-packages/bridgedb-0.6.5+0.gd9741cf.dirty-py2.7.egg/bridgedb/Bridges.py", line 295, in filterDistinctSubnets                                                      if bridge.address.version == 4:
AttributeError: 'NoneType' object has no attribute 'version'