[Bug]: When calling logger.data(), an 'undefined' is mysteriously added to the log output

[MatrixFrog]

The problem

I wrote a little test that demonstrates this: MatrixFrog@cb9ef9b The call to log.data() should be emitting '\x1B[90mdata\x1B[39m:test message\n' but instead we get '\x1B[90mdata\x1B[39m:undefinedtest message\n'

From what I can tell, the 'undefined' is coming from here: https://github.com/winstonjs/logform/blob/master/pad-levels.js#L64 though I'm not sure exactly why.

What version of Winston presents the issue?

3.5.1

What version of Node are you using?

14.17.6

If this worked in a previous version of Winston, which was it?

No response

Minimum Working Example

https://github.com/MatrixFrog/winston/commit/cb9ef9b09510aae9dbb6caf3bb697014aced5f68

Additional information

No response

[MatrixFrog]

I think I found a fix, looks like maybe just a little copy/paste error: winstonjs/logform#135

[DABH]

Thanks, reviewed!