XRENDERING-621: Make rendering errors translatables and extendables

* add missing default implementation

xwiki-rendering-api/src/main/java/org/xwiki/rendering/util/ErrorBlockGenerator.java

@@ -62,7 +62,10 @@
      * @since 14.0RC1
      */
     @Unstable
-    boolean containsError(Block block);
+    default boolean containsError(Block block)
+    {
+        return false;
+    }
 
     /**
      * Generates error blocks to render an error in a wiki page.