fix property name

[AIIX]

Description

Does not allow the GUI to show up on more recent mycroft-gui because the property name in ui is wrong.

• Fix property name stopping as per fix in mycroft-gui

Type of PR

• [x] Bugfix
• [ ] Feature implementation
• [ ] Refactor of code (without functional changes)
• [ ] Documentation improvements
• [ ] Test improvements

[krisgesling]

Good spotting - thanks!