fixed bug, if you have not Smalrubot and use sensor('A0').value then occur an exception.
fixed bug, if you have not Smalrubot and use sensor('A0').value then occur an exception.

sada/smalruby,smalruby/smalruby,Ikuyadeu/smalruby,iguchi1124/smalruby,nishidayuya/smalruby