Changing the syntax of a codebox

[Qehremanov]

Version, Operating system
CherryTree version: 1.2.0
OS: Ubuntu 20.04.1
Desktop: Gnome

Describe the bug
Changing the syntax of a codebox multiple times will increase the amounts of the code box property window exponentially.
As a result, the number of windows you have to close increases each time.

To Reproduce
Steps to reproduce the behavior:

1. Create a codebox. (Shift + Alt + D)
2. Select the Codebox.
3. Right click on the codebox
4. Click on "Change Codebox Properties". (Shift + Alt + D)
5. Choose any language for syntax highlighting
6. Click "OK" button in the "Automatic Syntax Highlighting" window.
7. Click "OK" button in the "Edit CodeBox" window.
8. Repeat this process several times starting from step 2.

Screenshots