Javascript ES6 Promise error "Uncaught (in promise)"

I'm getting an error on Chrome Console, I do not fully understand what could be the reason.

Here is my sample code:

function sayHi() {
    return new Promise(function(resolve, reject) {
        console.log('Hi')
        reject('Not in the mood')
        setTimeout(() => {
            resolve()
        }, 20)
    })
}

sayHi().then(() => {
    console.log('Bye')
})

If you run this code on console you will see the Promise being rejected, which is an expected outcome. However, there is also an error message:

Uncaught (in promise) Bye Promise.then (async) (anonymous) @ VM374412:11

This error message won't be there if reject is removed from the sayHi function. But that must not be the intention of any developer to not have reject at all.

Are we supposed to ignore the error message, or is there something I have totally missed out?

Thanks.