OT: Dock Icon duplicates when launching my app

[Tiemo Hollmann TB]

Hello,

 

When launching my App from the dock icon, it duplicates itself to the right
side of the dock icons. After quitting my app the duplicated icon gets off
again.

I don't experience this behavior with other apps. What is "special" on my
rev app, or what did I do wrong? Is this just a "special behavior" or could
it lead to any problems?

I am missing Mac Know How.

Thanks for any hint

Tiemo