Invalid API Route Status/Body Response
In one of your API routes a 204 or 304 status code was used as well as sending a response body.
This is invalid as a 204 or 304 status code dictates no response body should be present.
Send an empty body when using a 204 or 304 status code or use a different status code while sending a response body.
Before
export default function handler(req, res) {
res.status(204).send('invalid body')
}After
export default function handler(req, res) {
res.status(204).send()
}