Ubuntu 16.04: "Filtering" and "Statistics" freeze notebook controls

[paulmueller]

Easy to reproduce:

• open ShapeOut
• select a notebook tab other than "Filtering" and "Statistics"
• load data into the session
• select "Filtering" or "Statistics"

The notebook does not correctly draw its contents. Although the buttons etc. seem to exist (are just not visible).

In "Filtering", this bug is caused when the HT.HyperTreeList is added to the panel. As this seems to be a linux bug only, I will not attempt a fix for now.