Editor : slopes with no gradient values can be save

[bgiuliana]

What happened?

When editing a slope, a message says that gradient is a required property. Despite this, it is possible to save modifications without defing the gradient value.

What did you expect to happen?

We should block the save untill the user defines gradient value

How can we reproduce it (as minimally and precisely as possible)?

1. Go to the editor module
2. Select a track and click on the edition button
3. Click to edit the slopes without defining the gradient
4. Click on the save button. A message saying "the modifications are saved" appears.

What operating system, browser and environment are you using?

• Browser: Chrome v110
• OS: Windows 10
• Env: Dgex dev

OSRD version (top right corner Account button > Informations)

5d29253