Skip "shift up children" if deleting whole exhibit

Fixes a bug where an exhibit is undeletable if slugs conflict somewhere
(and also avoids some pointless DB churn).

models/Exhibit.php

@@ -154,6 +154,7 @@ protected function _delete()
         //get all the pages and delete them
         $pages = $this->getTable('ExhibitPage')->findBy(array('exhibit'=>$this->id));
         foreach($pages as $page) {
+            $page->setFixChildrenOnDelete(false);
             $page->delete();
         }
         $this->deleteTaggings();

models/ExhibitPage.php

@@ -54,6 +54,13 @@ class ExhibitPage extends Omeka_Record_AbstractRecord
      */
     protected $_related = array('ExhibitPageBlocks' => 'getPageBlocks');
 
+    /**
+     * Whether to automatically shift the page's children up a level when the page is deleted.
+     *
+     * @var boolean
+     */
+    private $_fixChildrenOnDelete = true;
+
     /**
      * Define mixins.
      *
@@ -272,6 +279,10 @@ protected function _delete()
             }
         }
 
+        if (!$this->_fixChildrenOnDelete) {
+            return;
+        }
+
         //bump all child pages up to being children of the parent
         $childPages = $this->getChildPages();
         foreach($childPages as $child) {
@@ -347,4 +358,14 @@ public function getRecordUrl($action = 'show')
         return array('module' => 'exhibit-builder', 'controller' => 'exhibits', 
                      'action' => $action, 'id' => $this->id);
     }
+
+    /**
+     * Set whether to automatically shift the page's children up a level when the page is deleted.
+     *
+     * @param boolean $fix
+     */
+    public function setFixChildrenOnDelete($fix)
+    {
+        $this->_fixChildrenOnDelete = (bool) $fix;
+    }
 }