Fix #1111
Fix #1111

Why typing letters with liveSearch disabled, index was incorrect as it
wasn't taking dividers and dropdown-headers into account

emilmoe/bootstrap-select,chengky/bootstrap-select,TeleginS/bootstrap-select,wearespindle/select3,TeleginS/bootstrap-select,jesenko/bootstrap-select,JoachimZ/bootstrap-select,Burick/bootstrap-select,silviomoreto/bootstrap-select,emilmoe/bootstrap-select,Burick/bootstrap-select,tommydevdocs/bootstrap-select,iaesaudi/bootstrap-select,anhtranqs3/bootstrap4-select,JoachimZ/bootstrap-select,QthCN/bootstrap-select,silviomoreto/bootstrap-select,tommydevdocs/bootstrap-select,jesenko/bootstrap-select,anhtranqs3/bootstrap4-select,QthCN/bootstrap-select,chengky/bootstrap-select,iaesaudi/bootstrap-select,wearespindle/select3