Display fix

Trying to reproduce what Emile did in his PR, but correcting many bugs in the process.

Pros:
- The UNumberSelector field is well aligned
- The app doesn't crash for random reasons when closing
- There are no longer any error message when loading or deleting scenarios and conditions

Cons:
- I haven't had the time to include everything Emile has done in his PR
- I haven't found a way to correct the UImage bug with svg images, so there are still some error messages when the image is loaded

I believe that it is more important to have a fully functional demo for tomorrow than a half working demo that looks better. (IMHO)