Make bbs.spy fail if the argument is not a number.

Currently, when using str_cmds.js the command ``;spy die'' crashes the BBS.

src/sbbs3/js_bbs.cpp

@@ -1849,6 +1849,8 @@ js_spy(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
 	if((sbbs=(sbbs_t*)JS_GetContextPrivate(cx))==NULL)
 		return(JS_FALSE);
 
+	if(!JSVAL_IS_NUMBER(argv[0]))
+		return(JS_FALSE);
 	JS_ValueToInt32(cx,argv[0],&node_num);
 	sbbs->spy(node_num);