player: fix autofit/geometry related segfault

Back when runtime updating of autofit/geometry was added for wayland and
x11 (commits: 4445ac828d and
ced92ba607 respectively), the naive
assumption was that window-related geometry would always be available.
While this is true 99% of the time, this isn't a guarentee. It is
possible for certain things such as loading shaders to delay starting up
the player. This causes autofit/geometry options to be registered as a
runtime update and triggers VOCTRL_VO_OPTS_CHANGED. This ends up calling
some geometry-related functions but this happens before the actual
values are available. Hence, a nullptr was accessed which segfaults. At
least one user experienced this with a combination of options in wayland
but in theory the same thing could happen under x11.

The fix is simple. Just be sure to check that the required geometry is
available before doing any calculations. In wayland, this would be
wl->current_output. Additionally add an assert to set_geometry (we
should never use this function without wl->current_output) to be extra
sure. In x11, the check is on x11->window. Later when the reconfig for
each backend actually happens, the autofit/geometry set by the user
happens anyway so ignoring it in this case does no harm. Fixes #9381.

video/out/wayland_common.c

@@ -1370,6 +1370,7 @@ static int set_cursor_visibility(struct vo_wayland_state *wl, bool on)
 static void set_geometry(struct vo_wayland_state *wl)
 {
     struct vo *vo = wl->vo;
+    assert(wl->current_output);
 
     struct vo_win_geometry geo;
     struct mp_rect screenrc = wl->current_output->geometry;
@@ -1597,11 +1598,13 @@ int vo_wayland_control(struct vo *vo, int *events, int request, void *arg)
             if (opt == &opts->geometry || opt == &opts->autofit ||
                 opt == &opts->autofit_smaller || opt == &opts->autofit_larger)
             {
-                set_geometry(wl);
-                wl->window_size = wl->vdparams;
-                if (!wl->vo_opts->fullscreen && !wl->vo_opts->window_maximized)
-                    wl->geometry = wl->window_size;
-                wl->pending_vo_events |= VO_EVENT_RESIZE;
+                if (wl->current_output) {
+                    set_geometry(wl);
+                    wl->window_size = wl->vdparams;
+                    if (!wl->vo_opts->fullscreen && !wl->vo_opts->window_maximized)
+                        wl->geometry = wl->window_size;
+                    wl->pending_vo_events |= VO_EVENT_RESIZE;
+                }
             }
         }
         return VO_TRUE;

video/out/x11_common.c

@@ -1847,6 +1847,9 @@ static void vo_x11_set_geometry(struct vo *vo)
 {
     struct vo_x11_state *x11 = vo->x11;
 
+    if (!x11->window)
+        return;
+
     if (x11->opts->window_maximized) {
         x11->pending_geometry_change = true;
     } else {