[flutter_tools] attempt to fix .first crasher in web loading (#52301)

packages/flutter_tools/lib/src/web/chrome.dart

@@ -234,6 +234,9 @@ class ChromeLauncher {
       final HttpClientRequest request = await client.getUrl(base.resolve('/json/list'));
       final HttpClientResponse response = await request.close();
       final List<dynamic> jsonObject = await json.fuse(utf8).decoder.bind(response).single as List<dynamic>;
+      if (jsonObject == null || jsonObject.isEmpty) {
+        return base;
+      }
       return base.resolve(jsonObject.first['devtoolsFrontendUrl'] as String);
     } on Exception {
       // If we fail to talk to the remote debugger protocol, give up and return