Commit 46ca880fca made `@encode` skip fields that are made zero-sized by
`[[no_unique_address]]`. When iterating the fields, the index which is
passed to `getFieldOffset` failed to be incremented for those due to the
use of an early `continue`, so subsequent fields reported an incorrect
offset. This caused an assertion to be triggered in
`getObjCEncodingForStructureImpl`.
Fixes#71250
609fe2cb4b