This commit fixes 2 separate issues related to root nodes retrieval from
embedded views with `<ng-content>`:
1) we did not account for the case where there were no projectable nodes
for a given `<ng-content>`;
2) we did not account for the case where projectable nodes for a given
`<ng-content>` were represented as an array of native nodes (happens in
the case of dynamically created components with projectable nodes);
Fixes#35967
PR Close#36051
a576852ad9