Correct issues with malformed channel trees having descendant nodes of non-folder nodes

[bjester]

Observed behavior

While migrating public channels to the new public API data model, we discovered one channel that has an html5 content node acting as topic/folder, having additional descendant nodes underneath.

Problematic channels:

• b431ba9f16a3588b89700f3eb8281af0

Expected behavior

We prevent the ricecooker API from attaching children or descendants to nodes that are not topics/folders

User-facing consequences

Unknown

Errors and logs

#4136

[bjester]

Main change should be to add the defensiveness in the ricecooker APIs.

[vkWeb]

Will work on this.

[bjester]

Resolved in 63693d3