Specifying a Title and OptGroups creates a redundant divider

[tjmay1981]

Specifying the title attribute when optgroups are being used results in a redundant <li class="dropdown-divider optgroup-1div"> being added to the start of the list.

Reproduced in Firefox, Chrome and Microsoft Edge on Windows 10

bootstrap-select v1.13.12
jQuery v3.4.1
Bootstrap v4.4.1

Demonstrated here: https://plnkr.co/edit/RHA12B5OFfxR2jqg5EEQ?p=preview

This seems to be due to the programmatically added <option class="bs-title-option"> being considered as part of the genuine structure of the list.

[caseyjhol]

Released in v1.13.16!