Keep the space of the line-break note under the image box.

An invisible copy of the note sits under the image box, so the page
does not jump when the tabs change.

publish/style.css

@@ -146,8 +146,10 @@ div.note {
  * that the box keeps its size when the tabs change: at most 450px wide,
  * and 337px high. That is the 300px writing area, the 35px toolbar (26px
  * buttons, 1px margins, 3px padding and a 1px line) and the 2px border.
+ * An invisible copy of the note under the editor takes the same space
+ * under the box.
  */
-#uploadparent {
+#uploadparent > .upload {
   box-sizing: border-box;
   width: 100%;
   max-width: 450px;
@@ -155,11 +157,13 @@ div.note {
   overflow: auto;
   border: 1px solid #b8c9be;
   border-radius: 8px;
-  margin-bottom: 10px;
 }
-#uploadparent>div {
+#uploadparent > .upload > div {
   padding: 10px;
 }
+#uploadparent > .spacer {
+  visibility: hidden;
+}
 
 .yes {
   font-weight: bold;
@@ -336,7 +340,7 @@ ul.error-box li {
   }
   /* On a phone the editor toolbar wraps onto two lines of 42px (40px
      buttons and 1px margins), so the editor is 393px high */
-  #uploadparent {
+  #uploadparent > .upload {
     max-width: none;
     height: 393px;
   }
@@ -396,7 +400,7 @@ ul.error-box li {
  * (300px), so it wraps onto three lines and the editor is 435px high.
  */
 @media (max-width: 345px) {
-  #uploadparent {
+  #uploadparent > .upload {
     height: 435px;
   }
 }