If find.command is defined (e.g. find.command=grep -R -i --exclude=*.svn* --line-number "$(find.what)" $(find.directory)$(find.files)), then there is problem for directory or file with characters need to be escaped. I think also that final directory separator have to be given by FilePath::Directory() (allow to manage directories with space on the tail)
for example :
mkdir -p /tmp/directory\ with\ spaces\ /
I propose this patch.