Resize causes expandos to clip

[Stevenic]

Describe the bug

Resizing the dialog explorer causes the expandos to sometimes clip:

Version

https://github.com/microsoft/BotFramework-Composer-Nightlies/releases/tag/v1.1.1-nightly.178300.83c0804

[tonyanziano]

@beyackle can you please take a look at this issue with the other project tree issues?

[beyackle]

I'll take a look. I think it's a CSS problem.