TagCloseElements conform to inherited expectations

Throwing an exception on request for an id or attribute breaks several
functions like $form->findPositionByAttribute.

See issue #1312

inc/Form/TagCloseElement.php

@@ -34,11 +34,15 @@ class TagCloseElement extends ValueElement {
      * do not call this
      *
      * @param $id
-     * @return void
+     * @return string
      * @throws \BadMethodCallException
      */
     public function id($id = null) {
-        throw new \BadMethodCallException('You can\t add ID to closing tag');
+        if ($id === null) {
+            return '';
+        } else {
+            throw new \BadMethodCallException('You can\t add ID to closing tag');
+        }
     }
 
     /**
@@ -46,22 +50,30 @@ class TagCloseElement extends ValueElement {
      *
      * @param $name
      * @param $value
-     * @return void
+     * @return string
      * @throws \BadMethodCallException
      */
     public function attr($name, $value = null) {
-        throw new \BadMethodCallException('You can\t add attributes to closing tag');
+        if ($value === null) {
+            return '';
+        } else {
+            throw new \BadMethodCallException('You can\t add attributes to closing tag');
+        }
     }
 
     /**
      * do not call this
      *
      * @param $attributes
-     * @return void
+     * @return array
      * @throws \BadMethodCallException
      */
     public function attrs($attributes = null) {
-        throw new \BadMethodCallException('You can\t add attributes to closing tag');
+        if ($attributes === null) {
+            return array();
+        } else {
+            throw new \BadMethodCallException('You can\t add attributes to closing tag');
+        }
     }
 
     /**