Removed an instance of serverBusy that I had missed in the previous commit.

Author: dpvc

lib/mj-page.js

@@ -450,7 +450,6 @@ function GetPreviews() {
 //    do the next queued expression
 //  
 function TypesetDone(result,selector) {
-  serverBusy = false;
   if (timer) {clearTimeout(timer); timer = null}
   if (errors.length) {result.errors = errors}
   if (data.renderer === "None") {content.innerHTML = "<p></p>"}