private ExplorerNode getSingleNode() {
        if (isSingleDocRef()) {
            return explorerNodes.get(0);
        } else {
            throw new RuntimeException("Expecting one node, found " + NullSafe.size(explorerNodes));
        }
    }
Presenter for removing tags from multiple nodes.
See {@link ExplorerNodeRemoveTagsPresenter} for tag removal on multiple nodes.
stroom-core-client/src/main/java/stroom/explorer/client/presenter/ExplorerNodeRemoveTagsPresenter.java