#35 -jd option fails if directory does not exist

[Johan Kjellander]

A Varkon startscript may include the -jd option
on the commandline that starts Varkon. If the
directory pointed to does not exist Varkon will
still start and display the directory as the default
directory in the file selector dialog. This is an error. If the -jd directory does not exist Varkon
should issue an error message and exit or use
another directory as fallback.