The error message is not showing when the release action on a dataset is failing

[Palollo]

To reproduce the problem:
one way to produce an error message is setting the "previous version" of the dataset with the same dataset as another one in draft state.
Then the backend server returns a message like this:

There are more than one draft datasets selected as the next version for the same dataset: [...]. Please delete or change the previousId in some of them (only one can be the next version) .

But the web interface is not showing it.

[Palollo]

The same when publish action: #22