drm/amd/display: add pp_smu NULL pointer check

add pp_smu NULL ptr check
Signed-off-by: Charlene Liu <charlene.liu@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1395,7 +1395,7 @@ static void notify_display_count_to_smu(
 	 * sent as part of pplib_apply_display_requirements.
 	 * So just return.
 	 */
-	if (!pp_smu->set_display_count)
+	if (!pp_smu || !pp_smu->set_display_count)
 		return;
 
 	display_count = 0;