Disable/gray-out the "remove selected" button when nothing to remove

[Robert Leach]

I noted when I was debugging a color slider issue that I could not remove sliders when there were only 2 present. That's fine, and this is a trivial enhancement suggestion, but I think it might be easy to disable the button when it will no longer do anything.

[Robert Leach]

Removing milestone: Color settings (automated comment)

[Christopher Keil]

@hepcat72

I am checking some of the color issues if they are still relevant after the recent color PR merge. This issue seems to be resolved for me. When there are only boundary thumbs present (2 thumbs) or no thumb is selected, then the button is always grayed out. Can you confirm that and given that no issue is extant, resolve this issue?

[Robert Leach]

Appears to have been fixed via another issue.

[Robert Leach]

Merged to master.