My code is as follows: (node.js code)

```
'use strict';

var Promise = require('bluebird');

function promised()
{
    return Promise.resolve();
}

function backgroundJob()
{
    return Promise.resolve();
}

function doBackgroundJob()
{
    // this is an intentional runaway promise.
    backgroundJob()
    .catch(function (err)
    {
        console.log('error', err);
    });
}

function test()
{
    return promised()
    .then(function ()
    {
        doBackgroundJob();
        return null;  // without this, bluebird displays the warning
    });
}

```

`doBackgroundJob()` does a background job, so it does not need to return a promise. But since it creates a promise, when the function is called in a `then()`, without an explicit `return null` in the `then()`, bluebird prints the following warning to the console. 'Warning: a promise was created in a handler but was not returned from it'.

This is somewhat unfair, since the caller does not need to know that the function uses a promise. How can I let bluebird to ignore the warning without `return null` in the `then()` in the caller?

I don't want to disable the warning, since it is quite useful.