Allow 0 as a term name.

mappers/taxonomy.inc

@@ -78,7 +78,9 @@ function taxonomy_feeds_processor_targets_alter(&$targets, $entity_type, $bundle
  * @todo Do not create new terms for non-autotag fields.
  */
 function taxonomy_feeds_set_target($source, $entity, $target, $terms, $mapping = array()) {
-  if (empty($terms)) {
+
+  // Allow mapping the string '0' to a term name.
+  if (empty($terms) && $terms != 0) {
     return;
   }
 

plugins/FeedsTermProcessor.inc

@@ -42,7 +42,7 @@ class FeedsTermProcessor extends FeedsProcessor {
    * Validates a term.
    */
   protected function entityValidate($term) {
-    if (empty($term->name)) {
+    if (drupal_strlen($term->name) == 0) {
       throw new FeedsValidationException(t('Term name missing.'));
     }
   }