If a print job with a zero-length control file is somehow created, lpd attempts to print the job and dies. lpd should either ignore or clean up the print job without dying.
lpr-0.50-1 dies in general if looked at funny. Does it persist in 0.50-2 as well?
Yes, the problem persists in lpr-0.50-2 lpq does not report any job information and pauses for a long time. It should report "Empty control file" or some such, and the job number, so that it can be lprm'd lpd deletes the control file (but not the data file) and dies.
Try 0.50-4