gh-113842: Add missing error check for PyIter_Next() in Python/symtable.c (GH-113843)

Python/symtable.c

@@ -977,6 +977,12 @@ update_symbols(PyObject *symbols, PyObject *scopes,
         }
         Py_DECREF(name);
     }
+
+    /* Check if loop ended because of exception in PyIter_Next */
+    if (PyErr_Occurred()) {
+        goto error;
+    }
+
     Py_DECREF(itr);
     Py_DECREF(v_free);
     return 1;