Use monospace font for unhandled errors

The browsers uses crude layout formatting that expects this.

app/error-handler.js

@@ -6,16 +6,6 @@
 (function(){
     "use strict";
 
-    function convertNewlines(msg, parentElem) {
-        const lines = msg.split("\n");
-        lines.forEach(function (line) {
-            parentElem.appendChild(document.createElement("br"));
-            parentElem.appendChild(document.createTextNode(line));
-        });
-        parentElem.removeChild(parentElem.firstChild);
-        return parentElem;
-    }
-
     // Fallback for all uncought errors
     function handleError (event, err) {
         try {
@@ -28,7 +18,7 @@
 
             var div = document.createElement("div");
             div.classList.add('noVNC_message');
-            convertNewlines(event.message, div);
+            div.appendChild(document.createTextNode(event.message));
             msg.appendChild(div);
 
             if (event.filename !== undefined && event.lineno !== undefined && event.colno !== undefined) {