qcacld-3.0: Check for NULL pointer

Check for NULL pointer before accessing.

Change-Id: I7916a475be98cb63cc8569f8eba022d5b49f5c10
CRs-Fixed: 2669232

core/hdd/src/wlan_hdd_main.c

@@ -3149,6 +3149,9 @@ static bool hdd_is_cac_in_progress(void)
 {
 	struct hdd_context *hdd_ctx = cds_get_context(QDF_MODULE_ID_HDD);
 
+	if (!hdd_ctx)
+		return false;
+
 	return (hdd_ctx->dev_dfs_cac_status == DFS_CAC_IN_PROGRESS);
 }