cannot strip a strange change set: with //

[Uwe Brauer]

Hi

There seems to be a bug of sort caused maybe of the combination of
mercurial version (still 5.2) and the evolve extension using topics. 

Sometimes I obtain change sets of the sort 
◍  changeset:   395:af4e475039d8
│╲   Branch:      default//examenjun
│ │  tag:         tip
│ │  Author:      Uwe Brauer <oub at mat.ucm.es>
│ │  Date:        Thu, 24 Jun 2021 17:00:53 +0200
│ │  Topic:       examenjun
│ │  Phase:       draft
│ │  Summary:     Another merge, hopefully succesful now
│ │
│ ○  changeset:   394:15d56fbc7202
│ │  Branch:      default
│ │  Author:      Uwe Brauer <oub at mat.ucm.es>
│ │  Date:        Thu, 24 Jun 2021 16:50:37 +0200
│ │  Topic:       examjunio
│ │  Phase:       draft
│ │  Summary:     Finish spanish version


Please note the  // so it seems that the topic is somehow combined with
the branch to new branch of sorts.

Usually I either run hg uncommit or simply strip. This time  I did not
pay attention and merged that branch into the default branch causing a
mess.

 hg strip -r 395 gives

abort: unknown revision 'default//examenjun'!

Any idea what to do?

Regards

Uwe Brauer