withFilter with rejected promise is considered False, hides errors

you can use a (promise-boolean)-returning function as your filter-function in withFilter.
considering a promise-boolean, the returned value can be three things:

1. resolved to True
2. resolved to False
3. rejected

the code currently considers case [3] as "False".

the problem happens when you use an `async` function as the filter-function, because when you have an error in your filter-function and an exception is thrown, you will never find out about it, because it becomes a rejected promise, which is considered simply "False".

it would be nice to somehow better handle this situation, perhaps doing a `console.error` when the promise is rejected, or mention this issue in the documentation, so that the users can put `try-catch` blocks around their with-filter code.

Start at the withFilter implementation and trace how a rejected promise from an async filter function is handled. The issue does not name a file or test, and it leaves the intended behavior unresolved between logging the rejection, documenting it, or changing error propagation; confirm that decision before adding coverage.

Written by the indexing model from the issue text.