when arguments are cells clear the locals slot (backport of #17927)

Objects/typeobject.c

@@ -6519,6 +6519,18 @@ super_init(PyObject *self, PyObject *args, PyObject *kwds)
             return -1;
         }
         obj = f->f_localsplus[0];
+        if (obj == NULL && co->co_cell2arg) {
+            /* The first argument might be a cell. */
+            n = PyTuple_GET_SIZE(co->co_cellvars);
+            for (i = 0; i < n; i++) {
+                if (co->co_cell2arg[i] == 0) {
+                    PyObject *cell = f->f_localsplus[co->co_nlocals + i];
+                    assert(PyCell_Check(cell));
+                    obj = PyCell_GET(cell);
+                    break;
+                }
+            }
+        }
         if (obj == NULL) {
             PyErr_SetString(PyExc_RuntimeError,
                             "super(): arg[0] deleted");