Don't mark function if no entry found

--HG--
extra : transplant_source : %B7i%C3h-%DD%E1d%14B%C3%924%07%2B%83%EF%F3%98s

Cython/Compiler/FlowControl.py

@@ -626,7 +626,8 @@ class CreateControlFlowGraph(CythonTransform):
         entry = node.entry
         if entry.is_anonymous:
             entry = self.env.lookup(node.name)
-        self.flow.mark_assignment(node, object_expr, entry)
+        if entry:
+            self.flow.mark_assignment(node, object_expr, entry)
         return self.visit_FuncDefNode(node)
 
     def visit_GeneratorBodyDefNode(self, node):