Checks the target and the source book before performing the sort.
Checks the target and the source book before performing the sort.

Signed-off-by: Abijeet <b16025a0a28f5bc92f04b832f9498ea3e8c34441@gmail.com>

Abijeet/BookStack,Abijeet/BookStack,BookStackApp/BookStack,BookStackApp/BookStack,Abijeet/BookStack,BookStackApp/BookStack