Fix for 'NoneType' object has no attribute 'author_sort' while trying to read a book (#2733)

cps/web.py

@@ -1516,7 +1516,6 @@ def profile():
 @viewer_required
 def read_book(book_id, book_format):
     book = calibre_db.get_filtered_book(book_id)
-    book.ordered_authors = calibre_db.order_authors([book], False)
 
     if not book:
         flash(_("Oops! Selected book is unavailable. File does not exist or is not accessible"),
@@ -1524,6 +1523,8 @@ def read_book(book_id, book_format):
         log.debug("Selected book is unavailable. File does not exist or is not accessible")
         return redirect(url_for("web.index"))
 
+    book.ordered_authors = calibre_db.order_authors([book], False)
+
     # check if book has a bookmark
     bookmark = None
     if current_user.is_authenticated: