fixes mongodb#835

Author: Pooya Parsa

src/Jenssegers/Mongodb/Schema/Blueprint.php

@@ -236,7 +236,7 @@ public function sparse_and_unique($columns = null, $options = [])
         $options['sparse'] = true;
         $options['unique'] = true;
 
-        $this->index($columns, $options);
+        $this->index($columns, null, null, $options);
 
         return $this;
     }