Custom scrollbar for huge tree makes the mouse jump on first click

[AnujaK]

1. Select a request and click on box to edit request name in 3rd column. Now select another request in second column. Issue: The request name in 3rd column does not change. It continues showing editable box.
2. The first time when we click on any node in a big tree(with many requests/folders in it), the project name (root) gets selected. In brief, mouse jumps the first time when we click on any node in a huge tree.

[AnujaK]

Task no. 1 of the above has been fixed. Updating the title of task.

[AnujaK]

Assigning to @rka12