exchange: fix test for remote support of binary phases

If the remote do not support phases, the "get" call will return None. We
change that default return to empty tuple to fix the membership testing.

This was a bug in the initial series. Thanks to yuja for catching this.

mercurial/exchange.py

@@ -1353,7 +1353,8 b' def _pullbundle2(pullop):'
 
     ui = pullop.repo.ui
     legacyphase = 'phases' in ui.configlist('devel', 'legacy.exchange')
-    if (not legacyphase and 'heads' in pullop.remotebundle2caps.get('phases')):
+    hasbinaryphase = 'heads' in pullop.remotebundle2caps.get('phases', ())
+    if (not legacyphase and hasbinaryphase):
         kwargs['phases'] = True
         pullop.stepsdone.add('phases')