Fix a possbile refleak in setint() of mmapmodule.c (GH-16136)

diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index 51ab3f0..0c64163 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -1468,7 +1468,8 @@
 setint(PyObject *d, const char *name, long value)
 {
     PyObject *o = PyLong_FromLong(value);
-    if (o && PyDict_SetItemString(d, name, o) == 0) {
+    if (o) {
+        PyDict_SetItemString(d, name, o);
         Py_DECREF(o);
     }
 }