“Non-contiguous selection” alert is avoidable

When attempting to stage a non-contiguous selection, an alert is presented (see screen shot). Rather than admonish the user after the fact, the alert can be avoided by simply not enabling the “Stage Lines” button under disallowed circumstances. That is to say, if ST is incapable of staging a discontiguous selection, the “Stage Lines” button should be disabled when there is a discontiguous selection.