Fix exception in APIRequest.
Fix exception in APIRequest.

Can sometimes be triggered if you delete a book, then quickly switch to a new collection. (Triggered at the collection selection screen).
gmartin7/myBloomFork,BloomBooks/BloomDesktop,gmartin7/myBloomFork,StephenMcConnel/BloomDesktop,gmartin7/myBloomFork,StephenMcConnel/BloomDesktop,StephenMcConnel/BloomDesktop,gmartin7/myBloomFork,BloomBooks/BloomDesktop,gmartin7/myBloomFork,BloomBooks/BloomDesktop,BloomBooks/BloomDesktop,gmartin7/myBloomFork,BloomBooks/BloomDesktop,StephenMcConnel/BloomDesktop,StephenMcConnel/BloomDesktop,StephenMcConnel/BloomDesktop,BloomBooks/BloomDesktop