gh-148651: Fix refcount leak in _zstd decompressor options (#148657)

The option parsing in Modules/_zstd/decompressor.c had a missing Py_DECREF(value) before the early return -1 when PyLong_AsInt(key) fails. The identical code in Modules/_zstd/compressor.c line 158 has the fix.

Author: mjbommar

Misc/NEWS.d/next/Library/2026-04-16-13-30-00.gh-issue-148651.ZsTdLk.rst

@@ -0,0 +1,2 @@
+Fix reference leak in :class:`compression.zstd.ZstdDecompressor` when an
+invalid option key is passed.

Modules/_zstd/decompressor.c

@@ -111,6 +111,7 @@ _zstd_set_d_parameters(ZstdDecompressor *self, PyObject *options)
         int key_v = PyLong_AsInt(key);
         Py_DECREF(key);
         if (key_v == -1 && PyErr_Occurred()) {
+            Py_DECREF(value);
             return -1;
         }