Move UI-WELCOME_ERROR from a script insertion to a hidden <div>

* store the error message in an extra div for later retrieval

Fixes: #10580

src/ui/views/ui_app.jade

@@ -34,6 +34,10 @@ block content
       box-shadow: inset -10px 0 20px -10px rgba(0, 0, 0, 0.5);
     }
 
+    #kibanaLoader__error {
+      display: none;
+    }
+
     .kibanaLoader__content {
       display: -webkit-box;
       display: -webkit-flex;
@@ -94,9 +98,12 @@ block content
         .kibanaWelcomeLogo
       .kibanaLoader__content
         | #{i18n('UI-WELCOME_MESSAGE')}
+      #kibanaLoader__error
+        | #{i18n('UI-WELCOME_ERROR')}
 
   script.
     window.onload = function () {
+      var failureText = document.getElementById('kibanaLoader__error').innerText;
       var buildNum = #{kibanaPayload.buildNum};
       var cacheParam = buildNum ? '?v=' + buildNum : '';
       function bundleFile(filename) {
@@ -125,7 +132,7 @@ block content
           err.style['text-align'] = 'center';
           err.style['background'] = '#F44336';
           err.style['padding'] = '25px';
-          err.innerText = '#{i18n('UI-WELCOME_ERROR')}';
+          err.innerText = failureText;
 
           document.body.innerHTML = err.outerHTML;
         }