Index: content_taxonomy_autocomplete.module
===================================================================
--- a/content_taxonomy_autocomplete.module
+++ b/content_taxonomy_autocomplete.module
@@ -153,9 +153,11 @@
   $terms = array();
   if (count($element['#default_value'])) {
     foreach ($element['#default_value'] as $delta => $entry) {
+      if ($entry[$field_key]) {
-      $terms[] = taxonomy_get_term($entry[$field_key]);
-    }
-  }
+        $terms[] = taxonomy_get_term($entry[$field_key]);
+      }
+    }
+  }
   $value = content_taxonomy_autocomplete_merge_tags($terms, $element['#vid']);
   $value = !empty($value) ? $value : NULL;
   return array($field_key => $value);
@@ -244,9 +246,9 @@
  * to the format to be stored in the field
  */
 function content_taxonomy_autocomplete_form2data($extracted_ids, $field, $element) {
-  $existing_tids = is_array($extracted_ids['existing_tids']) ? $extracted_ids['existing_tids'] : array();
+  $existing_tids = isset($extracted_ids['existing_tids']) && is_array($extracted_ids['existing_tids']) ? $extracted_ids['existing_tids'] : array();
   $new_tids = array();
-  if (is_array($extracted_ids['non_existing_terms'])) {
+  if (isset($extracted_ids['non_existing_terms']) && is_array($extracted_ids['non_existing_terms'])) {
     if ($field['widget']['extra_parent']) {
       $new_tids = content_taxonomy_autocomplete_insert_tags($extracted_ids['non_existing_terms'], $field['widget']['extra_parent']);
     }