[3.14] gh-140272: Fix memory leak in _gdbm.gdbm.clear() (GH-140274) (GH-140285)

(cherry picked from commit f937468)

Co-authored-by: Shamil <ashm.tech@proton.me>

Author: miss-islington

Misc/NEWS.d/next/Core_and_Builtins/2025-10-17-23-58-11.gh-issue-140272.lhY8uS.rst

@@ -0,0 +1 @@
+Fix memory leak in the :meth:`!clear` method of the :mod:`dbm.gnu` database.

Modules/_gdbmmodule.c

@@ -678,8 +678,10 @@ _gdbm_gdbm_clear_impl(gdbmobject *self, PyTypeObject *cls)
         }
         if (gdbm_delete(self->di_dbm, key) < 0) {
             PyErr_SetString(state->gdbm_error, "cannot delete item from database");
+            free(key.dptr);
             return NULL;
         }
+        free(key.dptr);
     }
     Py_RETURN_NONE;
 }