Old group label don't disappear - Sketch 55.2
Today I noticed that some old group label are stuck on the symbol page. They won't disappear and I can't delete them. They are not in any level.

<img width="816" alt="Schermafbeelding 2019-07-15 om 16 11 43" src="https://user-images.githubusercontent.com/52924147/61222605-509e0680-a71b-11e9-95c4-02e909d0faf0.png">
