Fix GH-16770: Tracing JIT type mismatch when returning UNDEF

When returning an UNDEF value, it actually becomes NULL.
The following code took this into account:
https://github.com/ph

Fix GH-16770: Tracing JIT type mismatch when returning UNDEF

When returning an UNDEF value, it actually becomes NULL.
The following code took this into account:
https://github.com/php/php-src/blob/28344e0445bc2abae8dc5f1376aa0ff350e6d66d/ext/opcache/jit/zend_jit_trace.c#L2196-L2199

But the stack does not update the type to NULL, causing a mismatch.

Closes GH-16784.

Co-authored-by: Dmitry Stogov <dmitry@zend.com>

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