Don't take over the screen if there's no window manager.
 [rsc] --rw-rw-r-- M 320859 glenda sys 15984 Oct 27 11:09 sys/src/cmd/auth/factotum/fgui.c
	/n/sourcesdump/2005/1027/plan9/sys/src/cmd/auth/factotum/fgui.c:76,82 - 
	/n/sourcesdump/2005/1028/plan9/sys/src/cmd/auth/factotum/fgui.c:76,83
	  	ARGBEGIN{
	  	}ARGEND;
	  
	- 	newwindow("-hide");
	+ 	if(newwindow("-hide") < 0)
	+ 		sysfatal("newwindow: %r");
	  
	  	fmtinstall('A', _attrfmt);