player/misc: fix audio-only fallback when video init fails

--stop-playback-on-init-failure=no is documented to continue playback in
audio-only mode if video init fails. However, this does not function
properly after a080432: because video
is initialized first, if video init fails, ao_chain is still null.
As a result, !(mpctx->vo_chain || mpctx->ao_chain) is true, a playback
error is raised, so the playback ends and audio does not play.

Fix this by reverting that change, so it checks the tracks instead.

Fixes: a080432

player/misc.c

@@ -252,7 +252,8 @@ void error_on_track(struct MPContext *mpctx, struct track *track)
     if (track->type == STREAM_VIDEO)
         MP_INFO(mpctx, "Video: no video\n");
     if (mpctx->opts->stop_playback_on_init_failure ||
-        !(mpctx->vo_chain || mpctx->ao_chain))
+        (!mpctx->current_track[0][STREAM_AUDIO] &&
+         !mpctx->current_track[0][STREAM_VIDEO]))
     {
         if (!mpctx->stop_play)
             mpctx->stop_play = PT_ERROR;