disp: msm: sde: add null pointer check for encoder current master

During virt disable call, sde_enc master was used without checking
for null condition. It results in crash. This change adds required
null pointer check for sde encoder current master before dereferencing
to avoid crash.

Change-Id: I69ee17017712ea3549bfefce5975a564a5a8c2e9
Signed-off-by: Yojana <quic_yjuadi@quicinc.com>

msm/sde/sde_encoder.c

@@ -3091,6 +3091,10 @@ static void sde_encoder_virt_disable(struct drm_encoder *drm_enc)
 	}
 
 	sde_enc = to_sde_encoder_virt(drm_enc);
+	if (!sde_enc->cur_master) {
+		SDE_ERROR("Invalid cur_master\n");
+		return;
+	}
 	sde_conn = to_sde_connector(sde_enc->cur_master->connector);
 	SDE_DEBUG_ENC(sde_enc, "\n");