also str representation of unicode character is different.

See merge request !1860

  in addition to None, id can be an empty list on this case

See merge request !1858

The previous pattern of using click and then pause is fragile and seems
to be the cause for test failures.

Instead of disabling in javascript, which cause the button to be visible
for a few milliseconds, disable directly in the HTML file.

Do not hide "document properties", because it can be useful and it does
not hurt and "edit images" because we don't hide the buttons to edit
annotations either, so this is consistent.

The setter does this already so no change is expected, but these are API
misuses and they just look wrong.

Also, modernise syntax a bit.

   The JSONEditor relies on call async load for load promises. The current code waits for the promises to finish and throw errors explicitly.

    This allows the renderjs properly handle the error on the same chain of promises.

See merge request !1855