Be robust to current_prompt not returning a String.
Be robust to current_prompt not returning a String.

This happened by accident to me and it causes Pry to infiniloop

ooohiroyukiooo/pry,shockone/pry,icebreaker/pry,richo/pry,nju520/pry,caporta/pry,ngpestelos/pry,nju520/pry,geoffreylitt/pry,jasnow/pry,bronzdoc/pry,pvdb/pry,nju520/pry,josue804/debunker,deivid-rodriguez/pry,gfvcastro/pry,raeno/pry,tdg5/pry,shockone/pry,pvdb/pry,caporta/pry,scalixte-mdsol/pry,shockone/pry,printercu/pry,sferik/pry,caporta/pry,jasnow/pry,geoffreylitt/pry,85x14/pry,jasonm23/pry,gfvcastro/pry,bronzdoc/pry,josue804/debunker,ngpestelos/pry,tdg5/pry,icebreaker/pry,printercu/pry,scalixte-mdsol/pry,85x14/pry,jasnow/pry,tdg5/pry,scalixte-mdsol/pry,ooohiroyukiooo/pry,jasonm23/pry,ooohiroyukiooo/pry,raeno/pry,sideci-sample/sideci-sample-pry,jasonm23/pry,raeno/pry,85x14/pry,sferik/pry