hw/net/rocker: Avoid double-free of l2_flood.group_ids

In of_dpa_cmd_add_l2_flood(), we allocate memory for the group->l2_flood.group_ids array, freeing any previous array. However, in the error-exit path we free the group_ids memory but do not clear the pointer to NULL. This means that if the guest causes us to take the error-exit path and then later call the function again, we will try again to free the memory we already freed. Fix this by clearing the group_ids pointer in the error exit path, so we maintain the invariant of "either it points at allocated memory, or it is NULL" (both being valid to g_free()). Cc: qemu-stable@nongnu.org Fixes: dc488f88806 ("rocker: add new rocker switch device") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3253 Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Message-id: 20260324193530.375628-1-peter.maydell@linaro.org