`KeyError` crash when ripping unknown disc with `%N` in track template

[elomatreb]

I tried ripping a disc that was not yet added to MusicBrainz (with the --unknown option), and I had the following track_template: %%A - %%d/%%N-%%t %%n.

This then resulted in the following crash:

Traceback (most recent call last):
  File "/usr/bin/whipper", line 33, in <module>
    sys.exit(load_entry_point('whipper==0.10.0', 'console_scripts', 'whipper')())
  File "/usr/lib/python3.10/site-packages/whipper/command/main.py", line 56, in main
    ret = cmd.do()
  File "/usr/lib/python3.10/site-packages/whipper/command/basecommand.py", line 141, in do
    return self.cmd.do()
  File "/usr/lib/python3.10/site-packages/whipper/command/basecommand.py", line 141, in do
    return self.cmd.do()
  File "/usr/lib/python3.10/site-packages/whipper/command/cd.py", line 203, in do
    ret = self.doCommand()
  File "/usr/lib/python3.10/site-packages/whipper/command/cd.py", line 559, in doCommand
    _ripIfNotRipped(i + 1)
  File "/usr/lib/python3.10/site-packages/whipper/command/cd.py", line 420, in _ripIfNotRipped
    path = self.program.getPath(self.program.outdir,
  File "/usr/lib/python3.10/site-packages/whipper/common/program.py", line 244, in getPath
    return os.path.join(outdir, template % v_fltr)
KeyError: 'N'

Removing %%N from the template string allowed me to rip the disc successfully.

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