Fix zero length slice declaration in flowgraph/node.go (#12393)

Signed-off-by: NCongqi Xia <congqi.xia@zilliz.com>

internal/util/flowgraph/node.go

@@ -68,9 +68,8 @@ func (nodeCtx *nodeCtx) work() {
 			return
 		default:
 			// inputs from inputsMessages for Operate
-			inputs := make([]Msg, 0)
 
-			var res []Msg
+			var inputs, res []Msg
 			if !nodeCtx.node.IsInputNode() {
 				nodeCtx.collectInputMessages()
 				inputs = nodeCtx.inputMessages