Fix Library/GoldenCheetah bug

.. its complicated .. basically, if a local directory exists it will
   *always* be used for application settings.

.. when you run GC for the first time with a local Library/GoldenCheetah
   then the HOMEDIR_GC will not be set as there is no config in there

.. the code checks this setting for blanks (but that fails because the
   value actually returned is "0") and so the local library is set to the
   value returned "0"

.. but the local library doesn't exist so it falls back to opening from
   the default location but using config from Library/GoldenCheetah !

.. the next time you launch all this gets resolved and you use
   Library/GoldenCheetah with the settings you set the last time.

Fixes #936