运行FORTRAN代码时出现的Linux错误，其中包括“nullify”

I started learning FORTRAN a few days ago, and I've stumbled across an error when trying to 'nullify' a pointer. The code is compiled without any flaw, but I this is what it displays after inputing the variable. I also know the problem is caused by the 'nullify' command, because the program runs without any error if I comment the line.I started learning FORTRAN a few days ago, and