Don't crash when inferring nodes from with statements, with multiple context managers. Closes #18.

1 files changed, 2 insertions, 0 deletions

diff --git a/protocols.py b/protocols.py
index a26986c..e66b802 100644
--- a/protocols.py
+++ b/protocols.py
@@ -311,6 +311,8 @@ nodes.ExceptHandler.assigned_stmts = raise_if_nothing_infered(excepthandler_assi
 def with_assigned_stmts(self, node, context=None, asspath=None):
     if asspath is None:
         for _, vars in self.items:
+            if vars is None:
+                continue
             for lst in vars.infer(context):
                 if isinstance(lst, (nodes.Tuple, nodes.List)):
                     for item in lst.nodes: