if (groupMap.containsKey(groupKey)) {
group = groupMap.get(groupKey);
group.setFiles(ObjectUtils.defaultIfNull(fileIDs, Collections.emptySet()));
} else {
group = new DrawableGroup(groupKey, fileIDs, groupSeen);
<BUG>group.seenProperty().addListener((observable, oldSeen, newSeen) -> {
markGroupSeen(group, newSeen);</BUG>
});
groupMap.put(groupKey, group);
}

if (groupMap.containsKey(groupKey)) {
group = groupMap.get(groupKey);
group.setFiles(ObjectUtils.defaultIfNull(fileIDs, Collections.emptySet()));
} else {
group = new DrawableGroup(groupKey, fileIDs, groupSeen);
group.seenProperty().addListener((o, oldSeen, newSeen) -> {
markGroupSeen(group, newSeen);
});
groupMap.put(groupKey, group);
