color: don't crash on invalid status codes (issue2036)
If an unknown file with a newline appears in the status output, color
shouldn't raise a KeyError trying to parse second line in the filename.
# should print nothing
# should fail
abort: path 'b/x' is inside repo 'b'
abort: path 'b/x' is inside repo 'b'
# should fail
abort: path 'b/x' is inside repo 'b'
# should arguably print nothing
# should fail
abort: path 'b/a' is inside repo 'b'