Fix incorrect return value that causes book matching to run very slowly
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Merge branch 'master' of https://github.com/cbhaley/calibre
Bulk metadata edit: Fix getting cover from EPUB files that have no cover image by rendering the first page as the cover not working. Fixes #1374243 [Bulk Metadata "Set from ebook file(s)" when no cover image doesn't work](https://bugs.launchpad.net/calibre/+bug/1374243)
Edit Book: When creating an NCX file from the Edit Table of Contents tool, do not use uuids for element ids
Tag Browser: When renaming an item that is currently being searched for, remove the search indicator, as the search will no longer match the renamed item. Fixes #1374624 [Tag Browser: Behaviour after "Rename"](https://bugs.launchpad.net/calibre/+bug/1374624)
Tag Browser: Fix drag and drop of books onto a language not setting the language. Fixes #1373504 [Cannot set language by drag-and-drop](https://bugs.launchpad.net/calibre/+bug/1373504)