TYPO3 Core

I just ran into this problem as well.
It occured after clicking "collapse all". All susequent clicks on "expand all" or "collapse all" led to the following JavaScript error:

SvgTree.js?bust=1594979006:1387 Uncaught TypeError: Cannot read property 'setAttribute' of null
    at SelectTree.setExpandedState (VM1836 SvgTree.js:1387)
    at SelectTree.hideChildren (VM1836 SvgTree.js:1364)
    at Array.forEach (<anonymous>)
    at SelectTree.collapseAll (VM1836 SvgTree.js:1410)
    at TreeToolbar.collapseAll (VM1866 TreeToolbar.js:141)
    at HTMLButtonElement.dispatch (VM1800 jquery.js:5242)
    at HTMLButtonElement.elemData.handle (VM1800 jquery.js:5049)

Clicking on "hide/show unchecked items" restores the tree and functionality (until "collapse all" is clicked again).

Most probably related to https://review.typo3.org/c/Packages/TYPO3.CMS/+/62051

The method in question looks like

      setExpandedState: function(node) {
        document
          .getElementById('identifier-' + this.getNodeStateIdentifier(node))
          .setAttribute('aria-expanded', (node.hasChildren ? node.expanded : null));
      },

Thus, the error message means element having an identifier with identifier-... does not exist.
I'm not sure whether the mentioned change above should only be working in the page-tree.

I encountered this problem using TYPO3 10.4.5

The problem is, that the DOM nodes are generated on the fly, but the expand/collapse all did not check if the DOM node exists and tried to change the state, also for nodes not available in the DOM.

By the way, is there any way to expand the Categories tree when all nodes are collapsed (using collapse all)? I do not have the toggle arrow at the root of the category tree.
What is the expected behaviour? Should the root node not be collapsed?

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/65065

Patch set 3 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/65065

Patch set 1 for branch 10.4 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/65108