What effect does this have? I have been hoping for a while that there would eventually be a way to share with "all". Hopefully if that ever gets implemented it will be more intuitive than this, though...?

@ttemberg: indeed I discovered this bug while searching for a way to share a contact with all. As I need to share some contacts among all my users I'm developing a patch for a "public" attribute http://bugs.limesurvey.org/view.php?id=9469 I'd like to know if your use case is the same as mine.

@Gab79: That is EXACTLY what I was hoping for. In our scenario I would like to share all of the participants, and having people unable to edit/fix them is causing us all sorts of problems. For us it would be best if "share with public" was the default when adding a participant since not all our clerks understand what is involved.

The error in the sharePanel is because in the following code

        foreach ($records as $row)
        {
            $oShared = User::model()->getName($row['share_uid']); //for conversion of uid to human readable names
            $owner = User::model()->getName($row['owner_uid']);
            $aData->rows[$i]['id'] = $row['participant_id']."--".$row['share_uid']; //This is the unique combination per record
            $aData->rows[$i]['cell'] = array($row['firstname'], $row['lastname'], $row['email'], $oShared[0]['full_name'], $row['share_uid'], $owner[0]['full_name'], $row['date_added'], $row['can_edit']);
            $i++;
        }

we have a $row['share_uid'] == '0' when we iterate on the "null user share" and then there is no $oShared[0]

Denis, can you please check the suggested fix and implement it if it looks fine to you?
Feel free to assign this one to Carsten if you are unsure.

I never work on Participant except yesterday ;) (on 2.06). I don't know the code of Participant .

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=15782

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=15783

Version 2.06+ Build 150930 released

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=17448