cannot have value which evaluates to false

[TimSimpsonR]

I tried to create a config value that was null in stages where a feature wasn't used. This does not seem to be possible as at some point fleece evaluates the value for a given stage, and if it's false for any reason raises an error. Here's the stack trace:

  config-value:
    +development: ""
    +staging: false
    +production: :decrypt:ABCDEF9876543210
    +/.*/: null

null, "", and false all show an error like the following

Traceback (most recent call last):
  File "/Users/tim.simpson/.local/bin/fleece", line 11, in <module>
    sys.exit(main())
  File "/Users/tim.simpson/.local/venvs/fleece/lib/python3.6/site-packages/fleece/cli/main.py", line 37, in main
    getattr(module, 'main')(sys.argv[2:])
  File "/Users/tim.simpson/.local/venvs/fleece/lib/python3.6/site-packages/fleece/cli/config/config.py", line 460, in main
    parsed_args.func(parsed_args)
  File "/Users/tim.simpson/.local/venvs/fleece/lib/python3.6/site-packages/fleece/cli/config/config.py", line 343, in render_config
    stages, config = _read_config_file(args)
  File "/Users/tim.simpson/.local/venvs/fleece/lib/python3.6/site-packages/fleece/cli/config/config.py", line 272, in _read_config_file
    render=True)
  File "/Users/tim.simpson/.local/venvs/fleece/lib/python3.6/site-packages/fleece/cli/config/config.py", line 192, in _decrypt_item
    data = _decrypt_dict(data, stage=stage, key=key, render=render)
  File "/Users/tim.simpson/.local/venvs/fleece/lib/python3.6/site-packages/fleece/cli/config/config.py", line 213, in _decrypt_dict
    render=render)
  File "/Users/tim.simpson/.local/venvs/fleece/lib/python3.6/site-packages/fleece/cli/config/config.py", line 190, in _decrypt_item
    '"{}"'.format(key, stage))
ValueError: Key "config-value" has no value for stage "timsimpsonr"