Since merging #6339, we can no longer disable the file logger.
Previously, setting either --logfile-max-size 0 or --logfile-max-number 0 would disable the file logger.

This is additionally problematic because having --logfile-max-size 0 will instead rotate the file every single log line. Users using --logfile-compress will have the additional issue of a race condition between the file getting compressed and it being rotated, and so will see hundreds of:

Couldn't compress log file: File IO error: No such file or directory (os error 2)