Run Error: std::logic_error

[Aries-Wu]

Hi, I have successfully compiled main.cpp, but the following error occurs when I run it.

terminate called after throwing an instance of 'std::logic_error'
  what():  basic_string::_M_construct null not valid

I don't know how to fix it, I can't locate where the problem occurs, and I'm begging for your help.
Thank you very much.