- Added partial support for Index as primary keys

src/Repository.php

@@ -97,7 +97,7 @@ class Repository implements RepositoryInterface
         else {
             $pk = Ulmus::resolveEntity($this->entityClass)->getPrimaryKeyField();
 
-            if (count($pk) === 1) {
+            if ($pk && count($pk) === 1) {
                 $field = key($pk);
 
                 $this->select(Common\Sql::function('COUNT', Common\Sql::raw("DISTINCT " . $this->entityClass::field($field))));