drm/msm/sde: add check to fix null pointer dereference

Check if sde_enc->crtc exists before using the variable
to avoid possible NULL dereferences.

Change-Id: If7b56c3b3ad3525b3efc22b6536a2dc5c865da48
Signed-off-by: Lei Chen <chenlei@codeaurora.org>

msm/sde/sde_encoder.c

@@ -3109,7 +3109,7 @@ static void sde_encoder_virt_disable(struct drm_encoder *drm_enc)
 
 	/* reset connector topology name property */
 	if (sde_enc->cur_master && sde_enc->cur_master->connector &&
-			sde_enc->crtc->state->active_changed) {
+			sde_enc->crtc && sde_enc->crtc->state->active_changed) {
 		ret = sde_rm_update_topology(&sde_kms->rm,
 				sde_enc->cur_master->connector->state, NULL);
 		if (ret) {
@@ -5531,6 +5531,8 @@ int sde_encoder_update_caps_for_cont_splash(struct drm_encoder *encoder,
 				conn->base.id);
 	}
 
+	sde_enc->crtc = encoder->crtc;
+
 	ret = sde_rm_reserve(&sde_kms->rm, encoder, encoder->crtc->state,
 			conn->state, false);
 	if (ret) {