How to workaround frequently crash the plasma shell, Kubuntu 16.04 on VirtualBox (5.0.30).

I constantly got a plasmashell crash with segmentation fault 11, Kubuntu 16.04 on VirtualBox (5.0.30).

screenshot: Plasmashell crash

The dialog entitled ``Plasma'' shows the next information, too (Developer Information).

  Application: Plasma (plasmashell), signal: Segmentation fault
  Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
  [Current thread is 1 (Thread 0x2afa1a0a30c0 (LWP 1913))]
This looked random, I found a hint at https://bugs.kde.org/show_bug.cgi?id=363371 .
A summary is also at Frequently crash the plasmashell .

Following this hint, this is caused by the dynamic window thumbnail creation. Here is the working example of show informational Tips.

show informational Tips working example
But in my environment, I can crash when I make this informational Tips several times. Here is a workaround: disable show informational Tips. To do this, Use System settings. Workspace -- Desktop Behavior -- Workspace, and off the show informational Tips. You can see the screenshot of this window below.

Plasma setting: Off the show informational tips