Fix crash
Fix crash

If total_similarity does not change to something other than 0, the program crashes
Gustavo6046/ChatterBot,davizucon/ChatterBot,vkosuri/ChatterBot,DarkmatterVale/ChatterBot,Reinaesaya/OUIRL-ChatBot,Reinaesaya/OUIRL-ChatBot,gunthercox/ChatterBot,maclogan/VirtualPenPal