Don't render PID field unless a pid is present, as it displays the default collection object.

plugins/pidfield/pidfield.module

@@ -276,11 +276,14 @@ function theme_pidfield_formatter_default($element) {
   //return $element['#item']['safe'];
   $pid = $element['#item']['safe'];
 
-  module_load_include('inc', 'fedora_repository', 'api/fedora_item');
-  $item = new Fedora_Item($pid);
+  if(!empty($pid)) {
+    module_load_include('inc', 'fedora_repository', 'api/fedora_item');
+    $item = new Fedora_Item($pid);
 
-  return fedora_repository_get_items($pid);
-  //return $item->objectProfile->objLabel;
+    return fedora_repository_get_items($pid);
+    //return $item->objectProfile->objLabel;
+  }
+  return null;
 }
 
 /**