Display the reason for not saving drawer menus element field when it contains errors

Steps to reproduce:

1. write an element with errors, like incorrect imports
2. go to a Drawer menus and select one
3. edit the Element field in "Element binding" and choose the incorrect element
4. save work in progress

Observe that the value in the Element field is still the same

Expected: the save should display a message which explains why the element field was not correctly changed.

AC

• When the element contains errors, an error message is displayed below the element selection, saying

  This element contains errors. Please select another one before you can save your work.

• The pattern described above is similar for all custom element selectors in Designer