drm/client: Do not destroy NULL modes

'modes' in drm_client_modeset_probe may fail to kcalloc.  If this
occurs, we jump to 'out', calling modes_destroy on it, which
dereferences it.  This may result in a NULL pointer dereference in the
error case.  Prevent that.

Fixes: 3039cc0c0653 ("drm/client: Make copies of modes")
Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260224221227.69126-2-jonathan.cavitt@intel.com