Fix tuple_insert_static crash on non-normalized empty type

[lukaszsamson]

This PR makes a minimal change and instead of matching on none type asserts that static component has tuple and returns none() on everything else. Returning badtuple here would be incorrect. A few lines up the decision was made that we are dealing with a proper tuple

is_proper_tuple? = descr_key?(dynamic, :tuple) and tuple_only?(static)

dynamic component is a tuple, static is a non-normalized empty type, for which tuple_only? returns true

Alternative approach would be to normalize empty list/tuple/map components at construction but that's a bigger refactor I would not attempt

Fixes #15541

Assisted-by: Claude Opus 4.8