More null pointer follies in PWB/Graphics

[Guy Harris]

Whoops, here's one I missed.  Note that for all of these, your line numbers
may differ:

*** gutil.d/ptog.d/ptog.c.BAK	Thu May  2 10:09:18 1985
--- gutil.d/ptog.d/ptog.c	Sat Jul 20 18:09:39 1985
***************
*** 48,54
  	else argf=1;
  
  	while(argc-- > 1) {
! 		if( strcmp(*++argv,"-")==0 || !argf ) fpi=stdin;
  		else if( **argv!='-' ) {
  			if((fpi =fopen(*argv,"r")) == NULL) continue;
  		} else { argc++; continue; }

--- 48,54 -----
  	else argf=1;
  
  	while(argc-- > 1) {
! 		if( !argf || strcmp(*++argv,"-")==0 ) fpi=stdin;
  		else if( **argv!='-' ) {
  			if((fpi =fopen(*argv,"r")) == NULL) continue;
  		} else { argc++; continue; }