[Bug]: The "add terminal" button is not working.

### Apache Hop version?

2.18

### Java version?

17

### Operating system

Linux

### What happened?

If you close all terminals and try to click the "+" button, it won't work. It only works if you have one terminal open, and even then, it will add more terminals.

### Issue Priority

Priority: 3

### Issue Component

Component: Hop Gui