drm/amd/display: Added missing null checks

[why&how]
Add the missing null check before dereference for dc_stream_status*

Fixes: 2d5bb791 ("drm/amd/display: Implement update_planes_and_stream_v3 sequence")
Reviewed-by: Josip Pavic <josip.pavic@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Sohaib Nadeem <sohaib.nadeem@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc.c

@@ -4291,6 +4291,9 @@ static int initialize_empty_surface_updates(
 	struct dc_stream_status *status = dc_stream_get_status(stream);
 	int i;
 
+	if (!status)
+		return 0;
+
 	for (i = 0; i < status->plane_count; i++)
 		srf_updates[i].surface = status->plane_states[i];