fix: tighten browser URL collection order and error handling

Agent-Logs-Url: https://github.com/XTLS/Xray-core/sessions/84d72770-6ad0-447a-8d86-94d692972a05

Co-authored-by: RPRX <63339210+RPRX@users.noreply.github.com>

transport/internet/browser_dialer/dialer.go

@@ -75,16 +75,17 @@ func BeginCollectingDialerProxyURLs() error {
 	return nil
 }
 
-func RegisterDialerProxyURL(raw string) {
+func RegisterDialerProxyURL(raw string) error {
 	if !IsBrowserDialerProxy(raw) {
-		return
+		return nil
 	}
 	initMu.Lock()
 	defer initMu.Unlock()
 	if pendingURLs == nil {
-		pendingURLs = map[string]struct{}{}
+		return errors.New("browser dialer url collection is not initialized")
 	}
 	pendingURLs[raw] = struct{}{}
+	return nil
 }
 
 func ConfigureCollectedDialerProxyURLs() error {