add empty string

Author: gpibarra

src/Filters/FiltersBelongsTo.php

@@ -51,7 +51,7 @@ protected function filterNullValues(array $values): array
     {
         return array_filter(
             $values,
-            fn ($v) => ! in_array($v, [null, 0, 'null', '0'], true)
+            fn ($v) => ! in_array($v, [null, 0, 'null', '0', ''], true)
         );
     }