fix: includes '-' as filter option for each filter

src/User/Database/QualityList.php

@@ -102,7 +102,7 @@ class QualityList
 
     public static function asSelectOptions(): array
     {
-        $result = ['n/a' => null];
+        $result = ['n/a' => null, '-' => '-'];
         foreach (array_keys(static::$qualities) as $quality) {
             $result[$quality] = $quality;
         }