Logging improvement for VGC-ONOS-NBI

Change-Id: I901964b71f2509cc81c44a208e5f5c563efd9704
diff --git a/voltha-go-controller/onos_nbi/flowadapter.go b/voltha-go-controller/onos_nbi/flowadapter.go
index b31700d..232b457 100644
--- a/voltha-go-controller/onos_nbi/flowadapter.go
+++ b/voltha-go-controller/onos_nbi/flowadapter.go
@@ -109,14 +109,19 @@
 	vars := mux.Vars(r)
 	deviceID := vars["deviceId"]
 	flowIDStr := vars["flowId"]
-	logger.Debugw(ctx, "Received Get Flows specific to flowID and deviceID", log.Fields{"flowId": flowIDStr, "DeviceID": deviceID})
+	var flowID uint64
+	var parseErr error
 
-	flowID, parseErr := strconv.ParseUint(flowIDStr, 10, 64)
-	if parseErr != nil {
-		logger.Errorw(ctx, "Failed to parse flowIDStr from string to uint64", log.Fields{"flowIDStr": flowIDStr, "Reason": parseErr.Error()})
-		w.WriteHeader(http.StatusInternalServerError)
-		return
+	logger.Debugw(ctx, "Received Get Flows specific to flowID and deviceID", log.Fields{"flowId": flowIDStr, "DeviceID": deviceID})
+	if len(flowIDStr) > 0 {
+		flowID, parseErr = strconv.ParseUint(flowIDStr, 10, 64)
+		if parseErr != nil {
+			logger.Errorw(ctx, "Failed to parse flowIDStr from string to uint64", log.Fields{"flowIDStr": flowIDStr, "Reason": parseErr.Error()})
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
 	}
+
 	var flowResp FlowEntry
 	if len(deviceID) > 0 && len(flowIDStr) > 0 {
 		flow, err := fh.getFlow(deviceID, flowID)