MarkerSetImpl getMarkerSetAt(Address address) {
			for (MarkerSetImpl markers : IterableUtils.reversedIterable(markerSets)) {
				if (markers.displayInMarkerBar() && markers.contains(address)) {
					return markers;
				}
			}
			return null;
		}
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