fixed a bug that caused a runtime fault if 'cd' was issued without any arguments.
fixed a bug that caused a runtime fault if 'cd' was issued without any arguments.

KevinMGranger/go9p,lionkov/ninep,floren/go9p,nigifabio/go9p,nilium/go9p,nilium/go9p,KevinMGranger/go9p,nigifabio/go9p,floren/go9p,szhilkin/go9p,szhilkin/go9p,larsth/go9p,henesy/go9p,henesy/go9p,larsth/go9p,cleahcim/go9p,edahlgren/go9p,cleahcim/go9p