How to blacklist undefined actions

[nybroe]

When using FileSaver (https://github.com/eligrey/FileSaver.js/) to download files to disk, it creates an action which is an instance of FileSaver and not an action type - but the reducer catches this action and returns the state as default - this doesn't break anything, it just creates a logging saying "action @ 14:00:13.959 undefined (in 3.59 ms)".

I have tried to blacklist this action in the loggingOptions, setting the blacklist as follows:
filter: {
blacklist: ['undefined']
}

I have also tried the following combinations:

1)
filter: {
blacklist: ['file-saver']
}

2)
filter: {
blacklist: ['FileSaver']
}

None of the above excludes the logging in the console.
So my question is - how do I exclude undefined actions?

The logging looks like this:

[ernestomancebo]

The action seems to be an object instead of a string value, thus blacklist doesn't catch it. Could you please expand the action item logged?