Only create symlinks if they don't already exist

If the second parameter to ln is a directory (or link to one) it creates a symlink inside it (unless the -T) option is specified. Changed the loop so it only creates symlinks if they don't exist to avoid geting symlinks in the symlinked direcdtories linking to the symlinked directory. (Symlinkception!)
It was not inherited by anything, though I'm not sure why I messed with it.