MAGETWO-86025: magento/magento2#8114: "Save Block"-button on Add New Block...

MAGETWO-86025: magento/magento2#8114: "Save Block"-button on Add New Block silently ignores clicks if the content is empty. #1032

app/code/Magento/Ui/view/base/web/js/form/components/html.js

@@ -19,6 +19,7 @@ define([
             showSpinner:    false,
             loading:        false,
             visible:        true,
+            error:          false,
             template:       'ui/content/content',
             additionalClasses: {}
         },

app/code/Magento/Ui/view/base/web/templates/content/content.html

@@ -17,3 +17,5 @@
         <span repeat="8"/>
     </div>
 </div>
+
+<label class="admin__field-error" if="error" attr="for: uid" text="error"/>