Comics are added to the reading lists multiple times

[mcpierce]

Describe the bug
When viewing a reading list, each comic is shown multiple times even though there's only one record per comic in the list.

To Reproduce
Steps to reproduce the behavior:

1. Create a reading list.
2. Add a comic to the list.
3. The comic is shown more than once when viewing the reading list.

Expected behavior
Each comic should show up only once in each list that includes it.

Screenshots