Fix failure to catch errors parsing arguments to Context.temp_override

Resolve unhandled exception when invalid types for StructRNA arguments
were passed to temp_override(..).

source/blender/python/intern/bpy_rna_context.cc

@@ -658,7 +658,7 @@ static PyObject *bpy_context_temp_override(PyObject *self, PyObject *args, PyObj
                                                               pyrna_struct_as_ptr_or_null_parse,
                                                               &params.region);
     Py_DECREF(kwds_parse);
-    if (parse_result == -1) {
+    if (!parse_result) {
       Py_DECREF(kwds);
       return nullptr;
     }