Make sure disabling spell checker with -1 really works

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Drop unused code

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Log Dialog: When selection is required, disable OK button when reloading log list

The OK button will be enabled when the user selects one revision or the selection of previous selected commit can be restored.

(Fixes issue #1914)

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>