mesa/st: Fix leak in st_create_fp_variant

CID: 1643014 Resource leak
Signed-off-by: Corentin Noël <corentin.noel@collabora.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35474>

src/mesa/state_tracker/st_program.c

@@ -1242,6 +1242,7 @@ st_create_fp_variant(struct st_context *st,
    variant->base.driver_shader = st_create_nir_shader(st, &state);
    if (report_compile_error && state.error_message) {
       *error = state.error_message;
+      FREE(variant);
       return NULL;
    }