webfs: use new content-type in redirects
 [rsc] --rw-rw-r-- M 628694 glenda sys 9503 Apr 10 12:10 sys/src/cmd/webfs/http.c
	/n/sourcesdump/2006/0410/plan9/sys/src/cmd/webfs/http.c:37,44 - 
	/n/sourcesdump/2006/0411/plan9/sys/src/cmd/webfs/http.c:37,45
	  static void
	  contenttype(HttpState *hs, char *value)
	  {
	- 	if(hs->c->contenttype == nil)
	- 		hs->c->contenttype = estrdup(value);
	+ 	if(hs->c->contenttype != nil)
	+ 		free(hs->c->contenttype);
	+ 	hs->c->contenttype = estrdup(value);
	  }
	  
	  static void