minor paranoid fix for FTL_FNREDIR fatal bug test
minor paranoid fix for FTL_FNREDIR fatal bug test

bin/modernish:
- Revert a tiny part of 4b2fe29d: use '[' and not 'test' for the
  FTL_FNREDIR test, as test() *could* be some shell function before
  modernish is sourced.

modernish/modernish