Fix segmentation fault when JSON serializing a PeriodIndex

Fixes pandas-dev#46683

Author: roberthdevries

pandas/_libs/src/ujson/python/objToJSON.c

@@ -238,8 +238,9 @@ static PyObject *get_values(PyObject *obj) {
             PyErr_Clear();
         } else if (PyObject_HasAttrString(values, "__array__")) {
             // We may have gotten a Categorical or Sparse array so call np.array
+            PyObject *array_values = PyObject_CallMethod(values, "__array__", NULL);
             Py_DECREF(values);
-            values = PyObject_CallMethod(values, "__array__", NULL);
+            values = array_values;
         } else if (!PyArray_CheckExact(values)) {
             // Didn't get a numpy array, so keep trying
             Py_DECREF(values);

pandas/tests/io/json/test_ujson.py

@@ -23,6 +23,7 @@
     DatetimeIndex,
     Index,
     NaT,
+    PeriodIndex,
     Series,
     Timedelta,
     Timestamp,
@@ -1240,3 +1241,9 @@ def test_encode_timedelta_iso(self, td):
         expected = f'"{td.isoformat()}"'
 
         assert result == expected
+
+    def test_encode_periodindex(self):
+        # GH 46683
+        p = PeriodIndex(["2022-04-06", "2022-04-07"], freq="D")
+        df = DataFrame(index=p)
+        assert df.to_json() == "{}"