Recently, we found out Mentee overview module is failing (T372164), because it makes invalid requests. The API response was this:

{
  "error": "parameter-validation-failed",
  "name": "activedaysago",
  "value": "",
  "failureCode": "badinteger",
  "failureData": null,
  "errorKey": "badinteger",
  "messageTranslations": {
    "cs": "Invalid value \"\" for integer parameter \"activedaysago\".",
    "en": "Invalid value \"\" for integer parameter \"activedaysago\"."
  },
  "httpCode": 400,
  "httpReason": "Bad Request"
}

and it was occuring in the default view (without setting any filters). To avoid any future Regression, we should improve our testing suite to verify Mentee overview is making valid API requests, at least in the default window.

This regression was introduced in 1057374: build: Update eslint-config-wikimedia to 0.28.2, which changed $.extend to Object.assign (which handle undefined values differently). Within this task, we should ensure MenteeOverviewApi gets a response when undefined is passed to MenteeOverviewApi.setFilters as a value.