Running `devtools_tool serve` doesn't work

[eliasyishak]

When I tried to run the devtools_tool serve command on a fresh checkout (after running devtools_tool sync) of flutter/devtools, I get a white blank page in chrome when it finishes running.

In the chrome console, the below error message is also printed

DevTools version 2.34.0-dev.8.
main.dart.js:16296 No DTD uri provided from the server during initialization.
main.dart.js:16296 Failed to handle API message from server:

{"jsonrpc":"2.0","result":null,"id":"0"}

TypeError: null: type 'JSNull' is not a subtype of type 'FutureOr<String>'

[eliasyishak]

cc @kenzieschmoll @jacob314