Fix(Bootstrapper): Handle null bindings

- Update anonymous function to explicitly return string
- Handle null bindings in vsprintf function

Author: guanguans

src/Bootstrapper.php

@@ -133,7 +133,7 @@ protected function toSql(QueryExecuted $queryExecuted): string
         $pdo = $queryExecuted->connection->getPdo();
 
         return vsprintf($sqlWithPlaceholders, array_map(
-            static fn ($binding) => null === $binding ? 'NULL' : $pdo->quote($binding),
+            static fn ($binding): string => null === $binding ? 'NULL' : $pdo->quote($binding),
             $bindings
         ));
     }