Hide changeform navigation while initializing

jet/static/jet/css/_changeform.scss

@@ -710,6 +710,7 @@ form .related-widget-wrapper ul {
 }
 
 .changeform-navigation {
+  display: none;
   float: left;
   margin-bottom: 20px;
 
@@ -718,6 +719,10 @@ form .related-widget-wrapper ul {
     margin-right: 10px;
   }
 
+  &.initialized {
+    display: block;
+  }
+
   &-button {
     font-weight: bold;
     vertical-align: middle;