Unit test fix

Change-Id: I28c23ff3d0a3d622fd2341880c40fd2384356c49
diff --git a/rw_core/core/api/grpc_nbi_handler_test.go b/rw_core/core/api/grpc_nbi_handler_test.go
index ff6ff0b..f42117e 100755
--- a/rw_core/core/api/grpc_nbi_handler_test.go
+++ b/rw_core/core/api/grpc_nbi_handler_test.go
@@ -1277,7 +1277,7 @@
 
 	// Wait until a logical device is ready
 	var vlFunction isLogicalDevicesConditionSatisfied = func(lds *voltha.LogicalDevices) bool {
-		if lds == nil || len(lds.Items) != 1 {
+		if lds == nil || len(lds.Items) != 1 || lds.Items[0] == nil {
 			return false
 		}
 		// Ensure there are both NNI ports and at least one UNI port on the logical device