Patch for cmd.c

[Andrew V. Samoilov]

Hi,

this patch fixes rare and almost impossible off-by-one.
If user input is empty (""), these lines can do very bad thing:

    if (reg_exp_t [strlen(reg_exp_t) - 1] == PATH_SEP){
        dirflag = 1;
        reg_exp_t [strlen(reg_exp_t) - 1] = 0;
    }

It is almoust impossible to meet PATH_SEP before '\0', but sometimes it happens.


-- 
Regards,
Andrew V. Samoilov.