Bug: Loading feedback for new element corrupts current feedback loading

[CSchmitz81]

If feedback is loaded for a new element before the previous feedback loading completes, the feedback items for the previous request get lost. When the more feedback is loaded for the original element it doesn't return that page (only elements with less than 1 page of feedback were tested). This probably happens because the feedback items aren't added to the element's feedback list, but the offset is for some reason.

Steps to reproduce:

1. Open an element details dialog for an element with feedback (may need to be an element with < 1 page of feedback)
2. Close the details dialog before feedback is loaded
3. Open another element which hasn't had all feedback loaded, before the first element's feedback should have completed loading
4. Wait for the current element's feedback to finish loading (fine if element has no feedback) - this step may not be required
5. Close the element details dialog
6. Open the details dialog for the first element
7. Observe that the feedback isn't already loaded & the feedback loading sequence is showing
8. Wait for the feedback to finish loading
9. Observe that feedback is done loading and no feedback items are shown