sudoers_policy_store_result: Fix potential NULL pointer deref

sudo_get_gidlist() can return NULL value

Author: dTenebrae

plugins/sudoers/policy.c

@@ -813,6 +813,10 @@ sudoers_policy_store_result(struct sudoers_context *ctx, bool accepted,
 
 	/* Only use results from a group db query, not the front end. */
 	gidlist = sudo_get_gidlist(ctx->runas.pw, ENTRY_TYPE_QUERIED);
+	if (gid_list == NULL) {
+	    sudo_gidlist_delref(gidlist);
+	    goto oom;
+	}
 
 	/* We reserve an extra spot in the list for the effective gid. */
 	glsize = sizeof("runas_groups=") - 1 +