drm/amd/display: Fix potential nullptr error

[Why]
Fix surface/plane potential nullptr

[How]
add null check
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -5313,6 +5313,12 @@ enum surface_update_type dm_determine_update_type_for_commit(struct dc *dc, stru
 	struct dc_stream_update stream_update;
 	enum surface_update_type update_type = UPDATE_TYPE_FAST;
 
+	if (!updates || !surface) {
+		DRM_ERROR("Plane or surface update failed to allocate");
+		/* Set type to FULL to avoid crashing in DC*/
+		update_type = UPDATE_TYPE_FULL;
+		goto ret;
+	}
 
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
 		new_dm_crtc_state = to_dm_crtc_state(new_crtc_state);