Improved export UI.

When recipe builder steps provide no UI, no need for rendering a controlled subsection (which would cause a slight glitch when checking the step checkbox by expanding the div a few pixels).

src/Orchard.Web/Modules/Orchard.ImportExport/Views/EditorTemplates/ExportActions/BuildRecipe.cshtml

@@ -16,9 +16,11 @@
                 <label for="@stepId" class="forcheckbox">@exportStep.DisplayName</label>
             </legend>
             @Html.Hint(@exportStep.Description)
+            @if (exportStep.Editor != null) {
                 <div data-controllerid="@stepId">
                     @Display(exportStep.Editor)
                 </div>
+            }
         </fieldset>
         exportStepIndex++;
         if (exportStepIndex < Model.Steps.Count) {