Currently, when editing a Landing Page using the Landing Page Editor (in Platform UI), the validation errors from the tab "Basics" can be hidden when the user displays tab "Elements".
When something in the "Basics" tab doesn't pass the validation and that tab is folded, then when the user clicks "Publish" nothing happens on screen. The user can see what is wrong only after he clicks on "Basics" tab again.
As a User, I want to be able to see the errors regardless of which tab is active.

Steps to reproduce

1. Create new eZ Platform EE installation.
2. In the Platform UI, go to "Page" tab.
3. Edit "Home" Landing Page.
4. In the "Basics" tab, clear "Page Description" field.
5. Click on "Elements" tab. The "Basic" tab will fold automatically.
6. Click "Publish". Nothing will happen and there will be no visible indicator on screen as to what is wrong.