Wrong arguments set for additional launchers

If `arguments` field in additional launcher property file is set to empty value the arguments for this launcher get copied from the arguments of the main launcher.

To reproduce use three attached additional launcher files in jpackage command:
---
jpackage ... --name SecondaryLaunchersTest --package-type deb --arguments Duke --arguments is --arguments the --arguments King --add-launcher Baz2=./Baz2.properties --add-launcher foo=./foo.properties --add-launcher Bar=./Bar.properties
---

By some reason arguments of Baz2 launcher are not empty, but equal to arguments of the main launcher. Output cfg files attached.

Reproduced on Linux, but seems to be platform unrelated problem.