Relations seem to affect each other in odd ways

[SvanteRichter]

Okay this one is a bit odd, so hang with me. Tested on 3.0.11 and master.

To reproduce:

1. Setup a new bolt install.

2. Create user and log in.

3. Prefill the db with a bunch of records.

4. In the entries contenttype add a relation to entries, the relations block should look something like this:

       relations:
           pages:
             multiple: false
             order: title
             label: Select a page
           entries:
             multiple: false
             order: title
             label: Select an entry
   

5. Edit one of the entries with a higher id, like 4 or 5.

6. Set the entry relation to one of the lower id's like 2 and save:

7. Reload the page, notice that while the entry relation is saved just fine, under the "This record is related to the following Entries:" it will show that the entry is related to itself. That is oddity no. 1.

8. Now add a relation to pages with a higher id than the relation you added for entries, but an id that also exists as an entry. For example, lets set the relation to page no. 4 and then save.

9. Reload the page and see that the entry->entry relation has been set to no. 4 too, even though we did not change it.

10. If you go to the frontend and dump the record the relations are correct (entries->2, pages->4), but since the preselected relation in the backend is incorrect as soon as one saves the record again it sets both to no. 4 even though entries should have been set to no. 2.

Possibly related to #5541

[GwendolenLynch]

Ah … I think I know what this is!