nouveau: Fix null dereference in nouveau_pushbuf_destroy

This may happen if the Nouveau device fails to initialize before
the pushbuf is set up; the abort logic will call this either way.

Signed-off-by: Sam Edwards <CFSworks@gmail.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21611>
(cherry picked from commit 9de997bde67df43a9e10a05f9b48419ee4cfec25)
2 files changed