Fix issues in changed files

- Initializes $return in Process::insert
- Update the type hint of dba::fetch
- Remove unused $a parameter in worker_init()
- Fix uses

scripts/worker.php

@@ -6,8 +6,8 @@
  */
 
 use Friendica\App;
-use Friendica\Core\Worker;
 use Friendica\Core\Config;
+use Friendica\Core\Worker;
 
 // Ensure that worker.php is executed from the base path of the installation
 if (!file_exists("boot.php") && (sizeof($_SERVER["argv"]) != 0)) {