1620 printer crash

[rms47]

If the user prints, or more precisely, does carriage control to the 1620 while the printer is unattached, the simulator crashes. This is because the lpt_space routine is not guardbanded against an unattached file. The fix is simple:

t_stat lpt_space (int32 count, int32 sflag)
{
int32 i, cc;
--- add these lines ---
if ((lpt_unit.flags & UNIT_ATT) == 0) {                 /* not attached? */
    ind[IN_PRCHK] = 1;                                  /* pri check */
    return SCPE_UNATT;
}
--- end added lines ---
cct_ptr = (cct_ptr + count) % cct_lnt;                  /* adv cct, mod lnt */

Bob Supnik