[ticket/16955] Fix phpdoc annotations and return types

PHPBB3-16955

phpBB/phpbb/db/extractor/sqlite3_extractor.php

@@ -135,7 +135,7 @@ class sqlite3_extractor extends base_extractor
 	/**
 	* Writes closing line(s) to database backup
 	*
-	* @return null
+	* @return void
 	* @throws extractor_not_initialized_exception when calling this function before init_extractor()
 	*/
 	public function write_end()