Fix missing placeholder in the Slide app

www/slide/main.js

@@ -134,7 +134,7 @@ define([
             var $modal = $pad.contents().find('#modal');
             var $content = $pad.contents().find('#content');
 
-            Slide.setModal($modal, $content, $pad, ifrw);
+            Slide.setModal($modal, $content, $pad, ifrw, Messages.slideInitialState);
 
             var enterPresentationMode = function (shouldLog) {
                 Slide.show(true, $textarea.val());
@@ -240,7 +240,7 @@ define([
                 var shjson = stringifyInner(textValue);
 
                 module.patchText(shjson);
-                Slide.update(textValue || Messages.slideInitialState);
+                Slide.update(textValue);
 
                 if (module.realtime.getUserDoc() !== shjson) {
                     console.error("realtime.getUserDoc() !== shjson");
@@ -648,7 +648,7 @@ define([
                 updateMetadata(userDoc);
 
                 editor.setValue(newDoc || '');
-                Slide.update(newDoc || Messages.slideInitialState);
+                Slide.update(newDoc);
 
                 if (Visible.isSupported()) {
                     Visible.onChange(function (yes) {

www/slide/slide.js

@@ -18,6 +18,7 @@ define([
     var $modal;
     var $content;
     var $pad;
+    var placeholder;
 
     Slide.onChange = function (f) {
         if (typeof(f) === 'function') {
@@ -160,6 +161,7 @@ define([
 
     var update = Slide.update = function (content) {
         if (!Slide.shown) { return; }
+        if (!content) { content = placeholder; }
         var old = Slide.content[Slide.index];
         Slide.content = content.split(/\n\s*\-\-\-\s*\n/).filter(truthy);
         if (old !== Slide.content[Slide.index]) {
@@ -256,11 +258,12 @@ define([
         });
     };
 
-    Slide.setModal = function ($m, $c, $p, iframe) {
+    Slide.setModal = function ($m, $c, $p, iframe, ph) {
         $modal = Slide.$modal = $m;
         $content = Slide.$content = $c;
         $pad = Slide.$pad = $p;
         ifrw = Slide.ifrw = iframe;
+        placeholder = Slide.placeholder = ph;
         addEvent();
     };