Fixed implicitly nullable params (#6616)

Author: huangdijia

Diff for: src/Schema/Grammars/SQLiteGrammar.php

@@ -429,7 +429,7 @@ public function typeMultiPolygon(Fluent $column): string
         return 'multipolygon';
     }
 
-    protected function getIndexColumns(Connection $connection, string $tableName = null): array
+    protected function getIndexColumns(Connection $connection, ?string $tableName = null): array
     {
         $sql = <<<'SQL'
             SELECT t.name AS table_name,
@@ -460,7 +460,7 @@ protected function getIndexColumns(Connection $connection, string $tableName = n
     /**
      * @see http://ezcomponents.org/docs/api/trunk/DatabaseSchema/ezcDbSchemaPgsqlReader.html
      */
-    protected function getTableIndexesList(Connection $connection, array $tableIndexes, string $tableName = null): array
+    protected function getTableIndexesList(Connection $connection, array $tableIndexes, ?string $tableName = null): array
     {
         $indexBuffer = [];
 

Diff for: src/Schema/SQLiteBuilder.php

@@ -83,7 +83,7 @@ public function getIndexListing(string $table): array
      *
      * @param array|string $index
      */
-    public function hasIndex(string $table, $index, string $type = null): bool
+    public function hasIndex(string $table, $index, ?string $type = null): bool
     {
         $type = is_null($type) ? $type : strtolower($type);