Newly created annotations "disappear" from sidebar if there is an existing selection

[robertknight]

When a new annotation is created while there is an existing selection, the new annotation will "disappear" after it is saved. I put "disappear" in quotes because the annotation is still present and is saved, its just not visible because it isn't in the current selection.

To see the problem:

1. Create a new annotation and save it
2. Click on the corresponding highlight in the document. This will create a selection in the sidebar so that only the annotation created in step 1 is visible
3. Start creating another annotation and save it.

In Step 3 the draft annotation will appear in the sidebar in addition to the previously selected highlight. When the new annotation is saved however, it disappears and only the previously selected annotation is visible.

I believe this is currently expected, but I think it is not the desirable behavior. I think the new annotation created in step 3 should remain visible after it is saved.

[esanzgar]

I believe this is the same as https://github.com/hypothesis/product-backlog/issues/1212