disp: msm: sde: fix null pointer dereference issue

This changes fixes null pointer dereference issue.

Change-Id: I9a9628f1fb274aea86a15792ac85b8505f25d28f
Signed-off-by: Renchao Liu <[email protected]>

msm/sde/sde_color_processing.c

@@ -1828,7 +1828,7 @@ static void _sde_cp_dspp_flush_helper(struct sde_crtc *sde_crtc, u32 feature)
 	for (i = 0; i < num_mixers; i++) {
 		ctl = sde_crtc->mixers[i].hw_ctl;
 		dspp = sde_crtc->mixers[i].hw_dspp;
-		if (ctl && ctl->ops.update_bitmask_dspp_subblk) {
+		if (ctl && dspp && ctl->ops.update_bitmask_dspp_subblk) {
 			if (feature == SDE_CP_CRTC_DSPP_SB) {
 				if (!dspp->sb_dma_in_use)
 					continue;