always wrap for-iterator node in NextNode after analysing it (might have been replaced)

Cython/Compiler/Nodes.py

@@ -5599,8 +5599,7 @@ class ForInStatNode(LoopNode, StatNode):
             # looked up in the outer scope
             iterator_env = NonLocalScopeWrapper(iterator_env)
         self.iterator = self.iterator.analyse_expressions(iterator_env)
-        if self.item is None:
-            # Hack. Sometimes analyse_declarations not called.
+        # rewrap in NextNode
         import ExprNodes
         self.item = ExprNodes.NextNode(
             self.iterator, lives_in_outer_scope=self.first_in_genexp)