🚀 go-pugleaf

If you hand "sed" an empty file with the "-f" flag, the S5 "sed" gets
confused and acts as if no "-f" flag were given, and tries to parse the
argument after the filename as a "sed" script.  As somebody who noted
this bug elsewhere said:

	This bug affects, e.g., shell programs that build up temporary sed
	scripts, which may possibly be null, for use as filters.

The fix appears to have been in V7, so I guess S5 never got around to
picking it up.  The fix is:

*** sed.h.orig	Thu Jun 29 11:38:43 1989
--- sed.h	Thu Jun 29 11:39:01 1989
***************
*** 129,131 ****
--- 129,132 ----
  struct label    *search();
  char    *gline();
  char    *place();
+ char	compfl;

*** sed0.c.orig	Thu Jun 29 11:37:25 1989
--- sed0.c	Thu Jun 29 11:38:23 1989
***************
*** 119,125 ****
  		}
  
  
! 	if(rep == ptrspace) {
  		eargv--;
  		eargc++;
  		eflag++;
--- 119,125 ----
  		}
  
  
! 	if(compfl == 0) {
  		eargv--;
  		eargc++;
  		eflag++;
***************
*** 155,160 ****
--- 155,161 ----
  	int     i, ii;
  	struct label    *lpt;
  
+ 	compfl = 1;
  	op = lastre;
  
  	if(rline(linebuf) < 0)  return;