fix : formatBytes test fail

Author: Victowolf

packages/devtools_app/lib/src/screens/network/utils/http_utils.dart

@@ -37,7 +37,7 @@ int calculateHeadersSize(Map<String, Object?>? headers) {
 // Values are rounded to one decimal place for kB and MB.
 // Uses decimal (base-10) units to match Chrome DevTools.
 String formatBytes(int? bytes) {
-  if (bytes == null) return '-';
+  if (bytes == null || bytes < 0) return '-';
   if (bytes < 1000) return '$bytes B';
   if (bytes < 1000 * 1000) {
     return '${(bytes / 1000).toStringAsFixed(1)} kB';