Prevent hooks from being called multiple times.

includes/utilities.inc

@@ -126,8 +126,9 @@ function islandora_describe_repository($url = NULL) {
 function islandora_build_hook_list($hook, $pids = array()) {
   $hooks = array();
 
-  foreach ($pids as $model) {
-    $hooks[] = islandora_escape_pid_for_function($model) . '_' . $hook;
+  $pids = array_unique($pids);
+  foreach ($pids as $pid) {
+    $hooks[] = islandora_escape_pid_for_function($pid) . '_' . $hook;
   }
   $hooks[] = $hook;
 

islandora.module

@@ -515,7 +515,7 @@ function islandora_object_load($object_id) {
 function islandora_datastream_load($datastream_id, $object_id) {
   $object = islandora_object_load($object_id);
 
-  if(!$object) {
+  if (!$object) {
     return NULL;
   }
 
@@ -784,4 +784,4 @@ function islandora_post_delete_datastream(FedoraObject $object, $datastream_id)
   foreach (islandora_build_hook_list(ISLANDORA_POST_PURGE_DATASTREAM_HOOK, $object->models) as $hook) {
     module_invoke_all($hook, $object, $datastream_id);
   }
-}
+}