containers. Now it handles ARRAY frames by appending.
VarBuilder.addChildToTop
void addChildToTop() @safeAdds _current as a child of the top-of-stack container.
For TAG frames, uses _lastTagName as the key. Adds the current value to the top-of-stack container.
For TAG frames, uses _lastTagName as the key. For OBJECT frames without a tag name, this is a no-op (caller should use startMember/endMember for object keys). For ARRAY frames, appends the current value.
Note
M-17 fix - previously this silently dropped children for non-TAG