Unnecesary DOM updates are generated without a `parentId`

[davhm]

When using a TableContainer in a hash-routed view (might be partial cause?), the loaded UI will be broken by containing duplicated DOM nodes at the top level of the document.

Reproduction

No reliable reproduction steps have been identified. The client project where this bug appears is known and currently accesible by @tobiu

Analysis

Inspecting the DOM reveals too many top-level nodes are added. Logging reveals that several malformed DOM updates are arriving in the main thread, These updates contain nodes without a parentId, and thus they are inserted at the DOM's top-level. This breaks the UI.