fix: set default worker parameter (#22960)

Co-authored-by: Qiu Jian <qiujian@yunionyun.com>

pkg/appsrv/workers.go

@@ -188,6 +188,12 @@ func NewWorkerManager(name string, workerCount int, backlog int, dbWorker bool)
 }
 
 func NewWorkerManagerIgnoreOverflow(name string, workerCount int, backlog int, dbWorker bool, ignoreOverflow bool) *SWorkerManager {
+	if workerCount <= 0 {
+		workerCount = 1
+	}
+	if backlog <= 0 {
+		backlog = 128
+	}
 	manager := SWorkerManager{name: name,
 		queue:          NewRing(workerCount * backlog),
 		workerCount:    workerCount,