Default not to "inform customer" when merging tickets

[FantasticNerd]

Hi,
I inherited the Znuny-System I have to work with.
Most of the time I can change the things I need and everythings works fine.

But in my Setup the "Inform Customer" Checkbox in the Merge-Dialog is checked by default.

I found this in the forum:
viewtopic.php?t=28146

So it seems that the default is that the checkbox is not marked, correct?
In my conclusion that means that somebody must have set up the checkbox as default marked hardcoded.

Is there an "easy"-way to undo that?

Thanks for you help.

Best wishes
Dennis