SCXML editor does not save State transition event on initial state

When creating a very simple start chart, and naming the transition events, the initial transition event name is not saved. In the attached example, the `start` event is not visible, as can be seen in this screenshot. After reloading this file, the label is thus also gone. Manually adding the property in the XML not delete it, but it is also not used by the editor.

QTCREATORBUG-17108 somewhat relates to this (missing attribute notion)