Error on installing Documention on theme

I keep getting the same error on the Documention Install on all the themes i try - See Error Below.

I have 1 custom theme and the Elemenatl clone addon theme, and core themes. And they all give me the same error.

Add the same issue on last 2 Versions - now on 9.1.3

Line 238- $args[‘topicTreeID’] = $tree->getTreeID();

Call to a member function getTreeID() on null


        if ($this->cParentID) {
            $parent = Page::getByID($this->cParentID);
            $path = '{ccm:export:page:' . $parent->getCollectionPath() . '}';
        $data->addChild('cParentID', $path);
     * @param \SimpleXMLElement $blockNode The block node to import
     * @param Page|mixed $page This is ignored
     * @return array<string, mixed>
    public function getImportData($blockNode, $page)
        $args = [];
        $treeName = (string) $blockNode->data->tree;
        $page = (string) $blockNode->data->cParentID;
        $tree = TopicTree::getByName($treeName);

$args['topicTreeID'] = $tree->getTreeID();

$args['cParentID'] = 0;
        $args['title'] = (string) $blockNode->data->title;
        $args['mode'] = (string) $blockNode->data->mode;
        $args['titleFormat'] = (string) $blockNode->data->titleFormat;
        if (!$args['mode']) {
            $args['mode'] = 'S';
        if (!$args['titleFormat']) {
            $args['titleFormat'] = 'h5';

I have created my own custom theme using a V8 theme i had already which i updated to latest bootstape to match elemental - so as to use all the new features.

But to use the Boards system you seem to have to use documention?

Please advise ? As i dont actually need the documention pages etc on my theme. All I need it the abillity to add templates to the Boards Section? in order to use the new Layouts?

Thanks All