fix: release buffer on tp_alloc failure in vectorcall functions

When _parse_fastcall_args succeeds but tp_alloc subsequently fails,
the acquired buffer was leaked. Now release buf/buf_owner before
returning NULL in all four vectorcall functions.

Author: ifduyue

src/_xxhash.c

@@ -511,8 +511,11 @@ PYXXH32_vectorcall(PyObject *type, PyObject *const *args,
 
     PYXXH32Object *self = (PYXXH32Object *)
         ((PyTypeObject *)type)->tp_alloc((PyTypeObject *)type, 0);
-    if (self == NULL)
+    if (self == NULL) {
+        PyBuffer_Release(&buf);
+        Py_XDECREF(buf_owner);
         return NULL;
+    }
 
     self->xxhash_state = XXH32_createState();
     if (self->xxhash_state == NULL) {
@@ -871,8 +874,11 @@ PYXXH64_vectorcall(PyObject *type, PyObject *const *args,
 
     PYXXH64Object *self = (PYXXH64Object *)
         ((PyTypeObject *)type)->tp_alloc((PyTypeObject *)type, 0);
-    if (self == NULL)
+    if (self == NULL) {
+        PyBuffer_Release(&buf);
+        Py_XDECREF(buf_owner);
         return NULL;
+    }
 
     self->xxhash_state = XXH64_createState();
     if (self->xxhash_state == NULL) {
@@ -1227,8 +1233,11 @@ PYXXH3_64_vectorcall(PyObject *type, PyObject *const *args,
 
     PYXXH3_64Object *self = (PYXXH3_64Object *)
         ((PyTypeObject *)type)->tp_alloc((PyTypeObject *)type, 0);
-    if (self == NULL)
+    if (self == NULL) {
+        PyBuffer_Release(&buf);
+        Py_XDECREF(buf_owner);
         return NULL;
+    }
 
     self->xxhash_state = XXH3_createState();
     if (self->xxhash_state == NULL) {
@@ -1592,8 +1601,11 @@ PYXXH3_128_vectorcall(PyObject *type, PyObject *const *args,
 
     PYXXH3_128Object *self = (PYXXH3_128Object *)
         ((PyTypeObject *)type)->tp_alloc((PyTypeObject *)type, 0);
-    if (self == NULL)
+    if (self == NULL) {
+        PyBuffer_Release(&buf);
+        Py_XDECREF(buf_owner);
         return NULL;
+    }
 
     self->xxhash_state = XXH3_createState();
     if (self->xxhash_state == NULL) {