iwasm crashes when handling `ref.as_non_null` on `ref null noextern`

[akldc]

Test case

(module
  (type $0 (func (result (ref null noextern))))
  (export "main" (func 0))
  (func $0
    (type 0)
    (ref.null noextern)
    (ref.as_non_null)
  )
)

Describe the bug
The module attempts to convert a nullable noextern reference to a non-null one using ref.as_non_null. Since the operand is null, the expected runtime behavior is a trap: null reference.
However, when executing the module with iwasm, the engine fails during module loading with the following error:

$ iwasm -f main test1.wasm
WASM module load failed: insert ref type to hash set failed

This error occurs before execution and indicates an internal failure in the type construction or canonicalization phase, rather than a semantic trap.
The failure likely stems from an internal bug in iwasm’s type canonicalization or hash-consing logic for non-null GC reference types, specifically when constructing the heap type ref noextern produced by ref.as_non_null.

Version
iwasm 2.4.4
ubuntu 20.04

To Reproduce
Steps to reproduce the behavior:

1. Compile iwasm with flags like '-DWAMR_BUILD_JIT=1 -DWAMR_BUILD_TAIL_CALL=1 -DWAMR_BUILD_GC=1'
2. Run iwasm with CLI options like 'iwasm -f main test1.wasm'
3. See error

Expected behavior
wasm trap: null reference

Actual Result
WASM module load failed: insert ref type to hash set failed

Desktop (please complete the following information):

• Arch x86_64
• OS ubuntu 20.04