Add the page parameter to the islandora_tabs hook call.

...  Facilitates implementation of equivalent functionality, where
the object was instantiated with the PID, and then the page was
passed to the method declared in your ISLANDORACM stream.

fedora_repository.module

@@ -1071,7 +1071,7 @@ function fedora_repository_get_items($pid = NULL, $dsId = NULL, $collection = NU
    $object_details = array();
   }
 
-  $hook_tabs = module_invoke_all('islandora_tabs', $content_models, $pid);
+  $hook_tabs = module_invoke_all('islandora_tabs', $content_models, $pid, $page_number);
   $cmodels_tabs = array_merge($cmodels_tabs, $object_details, $hook_tabs);
 
   return tabs_render($cmodels_tabs);