Fixes to ACBF reading
Summary:
- Cleaned the code a bit.
- Fixed potential issues with some documents.
- Fixed characters element name.
Test Plan: Can read Pepper & Carrot 1 & 2 and some other acbf comics from fictionbook-lib.org.
Reviewers: Peruse, leinir
Reviewed By: Peruse, leinir
Subscribers: leinir
Differential Revision: https://phabricator.kde.org/D3984