Make the various iterators' "setstate" sliently and consistently clip the
index.  This avoids the possibility of setting an iterator to an invalid
state.
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 123df8c..f815595 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -998,8 +998,8 @@
     if (it->it_seq != NULL) {
         if (index < 0)
             index = 0;
-        else if (it->it_seq != NULL && index > PyTuple_GET_SIZE(it->it_seq))
-            index = PyTuple_GET_SIZE(it->it_seq);
+        else if (index > PyTuple_GET_SIZE(it->it_seq))
+            index = PyTuple_GET_SIZE(it->it_seq); /* exhausted iterator */
         it->it_index = index;
     }
     Py_RETURN_NONE;