When submitting a form with multiple checkbox values of the same group using the GET method, the browser is suppose to repeat the checkbox name with each value in the query parameter:

?name=value1&name=value2&name=value3

However, with helper.js enabled, only the last value gets appended to the query parameters:

?name=value3

This interferes with the server-side parameters parsing and will result in a NoConstructorMatched error.

Removing helper.js from Web/View/Layout.hs fixes this issue.