Web IDE: File navigator scrolls when clicking "New file" button

Summary

Small UI glitch, clicking on the + button in the left file navigation of the Web IDE scrolls down the list.

Steps to reproduce

• Click the + button in the Web IDE file navigation.
• Click the + button on folders in the Web IDE file navigation.

What is the current bug behavior?

If I click on the + button to create a new file (ide-new-btn), the side navigation scrolls down some px to the top border of the dropdown menu. See attached gif. Same applies to the + button on folders, here, the dropdown menu disappears again.

Tested on Chrome and Safari.

What is the expected correct behavior?

Scrolling position should be kept, dropdown menu should be correctly rendered on top.

cc @jramsay