update_check_packages: set check done if no opkg support available

Origin commit data
------------------
Commit: 59223efb01
Author: Thilo Graf <dbt@novatux.de>
Date: 2021-04-10 (Sat, 10 Apr 2021)

src/gui/update_check_packages.cpp

@@ -60,7 +60,10 @@ void CUpdateCheckPackages::check4PackageUpdates()
 
 	COPKGManager man;
 	if (!man.hasOpkgSupport())
+	{
+		check_done = true;
 		return;
+	}
 
 	man.setUpdateCheckResult(false);