avoid some dead code in generator exit

Cython/Compiler/Nodes.py

@@ -3849,9 +3849,11 @@ class GeneratorBodyDefNode(DefNode):
 
         # on normal generator termination, we do not take the exception propagation
         # path: no traceback info is required and not creating it is much faster
+        if not self.body.is_terminator:
             code.putln('PyErr_SetNone(PyExc_StopIteration);')
         # ----- Error cleanup
         if code.error_label in code.labels_used:
+            if not self.body.is_terminator:
                 code.put_goto(code.return_label)
             code.put_label(code.error_label)
             for cname, type in code.funcstate.all_managed_temps():