Fix "undefined" filename in error message if file doesn't exist

exec/typeasc.js

@@ -2,6 +2,8 @@
 
 // Convert plain-text with (optional) Synchronet attribute (Ctrl-A) codes to HTML
 
+// $Id: typeasc.js,v 1.8 2020/07/18 04:07:29 rswindell Exp $
+
 load("sbbsdefs.js");
 load("asc2htmlterm.js");
 var f;
@@ -34,7 +36,7 @@ for(i in argv) {
 				break;
 			default:
 				if(this.f==undefined) {
-					this.f = new File(file_getcase(argv[i]));
+					this.f = new File(file_getcase(argv[i]) || argv[i]);
 					filename=this.f.name.replace(/^.*[\\\/]/,'');
 				}
 		}