void insertSet(MarkerSetImpl set) {
			int index = Collections.binarySearch(markerSets, set);
			if (index < 0) {
				index = -(index + 1);
			}
			markerSets.add(index, set);
		}
Use this close listener approach instead of plugin events, since we don't get a
ProgramClosedPluginEvent when a trace view is closed, but we can listen for its
domain object closing, which works for plain programs, too.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/marker/MarkerManager.java