Issue #24683: Fixed a crash in _json.make_encoder() called with non-dict 1st argument.

Modules/_json.c

@@ -1850,6 +1850,13 @@ encoder_init(PyObject *self, PyObject *args, PyObject *kwds)
     if (allow_nan < 0)
         return -1;
 
+    if (markers != Py_None && !PyDict_Check(markers)) {
+        PyErr_Format(PyExc_TypeError,
+                     "make_encoder() argument 1 must be dict or None, "
+                     "not %.200s", Py_TYPE(markers)->tp_name);
+        return -1;
+    }
+
     s->markers = markers;
     s->defaultfn = defaultfn;
     s->encoder = encoder;