https://javafx-jira.kenai.com/browse/RT-22972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel

comboBox doesn't have empty Text property after this fix. Bug placeholder node description still contain mentioning of the emptyText:

This Node is shown to the user when the ComboBox has no content to show. The placeholder node is shown in the ComboBox popup area when the items list is null or empty. This is different than the emptyText property, which is shown in the ComboBox Button / TextField area when there is no user-input value.