Incorrect dialog & dropdown selector behavior

[bubafinder]

I'm submitting a...

• Bug report
• Regression (a behavior that used to work and stopped working in a new release)
• Feature request
• Documentation issue or request

Context

The dialog used for adding activity into the repository (Add, Add into, and Add below) activates the scroll after the dropdown selector is opened. The whole dialog including the dropdown selector is scrollable inside the same default height with a grey background.

Expected Behavior

After the dropdown selector is opened, options are extended outside the dialog, without activating the scroll.

Screencast