Index: primary_term.module
===================================================================
--- primary_term.module	(revision 20611)
+++ primary_term.module	(working copy)
@@ -109,6 +109,14 @@
 
         // Build the select list options from the terms within these vocabularies.
         $terms = array();
+
+        // If the primary term is not required add a blank entry to the terms.
+        if (!variable_get('pt_required_'. $form['type']['#value'], FALSE)) {
+          $blank_option = new stdClass;
+          $blank_option->option = array('' => t(' --Select-- '));
+          $terms[] = $blank_option;
+        }
+
         foreach ($type_vids as $vid) {
           if (in_array($vid, $vids) && primary_term_vocabulary_access($vid)) {
             $options = array();