qcacmn: Add null check while extracting tbtt qtime

The tbtt qtime value is given by target via WMI event.
This can be null when target doesn't give this buffer.
Add check in host to prevent null deference.

Change-Id: Id9b4a4093b0422a0337e4dabff1ca74ff0d0472e

wmi/src/wmi_unified_vdev_tlv.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2019 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2016-2020 The Linux Foundation. All rights reserved.
  *
  * Permission to use, copy, modify, and/or distribute this software for
  * any purpose with or without fee is hereby granted, provided that the
@@ -317,10 +317,12 @@ static QDF_STATUS extract_tbttoffset_update_params_tlv(
 		return QDF_STATUS_E_INVAL;
 	tbtt_param->tbttoffset =
 		param_buf->tbttoffset_list[tbtt_param->vdev_id];
-	tbtt_param->vdev_tbtt_qtime_lo =
-		param_buf->tbtt_qtime_low_us_list[tbtt_param->vdev_id];
-	tbtt_param->vdev_tbtt_qtime_hi =
-		param_buf->tbtt_qtime_high_us_list[tbtt_param->vdev_id];
+	if (param_buf->tbtt_qtime_low_us_list)
+		tbtt_param->vdev_tbtt_qtime_lo =
+		    param_buf->tbtt_qtime_low_us_list[tbtt_param->vdev_id];
+	if (param_buf->tbtt_qtime_high_us_list)
+		tbtt_param->vdev_tbtt_qtime_hi =
+		    param_buf->tbtt_qtime_high_us_list[tbtt_param->vdev_id];
 
 	return QDF_STATUS_SUCCESS;
 }