1) Wasm code is not associated with a Code object, hence
   WasmFrame::unchecked_code will always return a null object. Hence we
   can use the default implementation from TypedFrame and avoid the
   lookup on the heap which will always fail.
2) InternalFrame inherits from TypedFrame, hence can also reuse the
   unchecked_code implementation from TypedFrame.
3) Use "{}" instead of "Code()" to return "nothing".

R=jkummerow@chromium.org

Bug: v8:11074
Change-Id: I142d2f21c05bf87cafa5ba6e7f463510be6c70bb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2653229Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72410}