No icon on Plasma Linux

#### Actual behavior:
Hello @thedoublejay ,

as I told you on TG a while back, there is no icon on Plasma Linux. I don't know if that is a Plasma issue or one in your appimage.
This is what it looks like: https://i.imgur.com/MDWIBV9.png

#### Expected behavior:
Have the actual icon available on the top left of the wallet, but also in the task manager.

#### How to reproduce it (as minimally and precisely as possible):
Start the wallet on Linux, maybe KDE Plasma is required for this, maybe X11 as well, not sure exactly but somehow I doubt it.

#### What are your environment parameters?

- DeFi Wallet Version: 2.5.2
- Operating System (OS): Arch Linux AMD64
- Current free storage capacity: More than enough

#### Anything else we need to know?
It's low priority, but I think it would look much better to potential users.