Fails to parse valid spectest modules

[nagisa]

Describe the Bug

walrus will fail to parse some of the valid spec-tests. In particular I found it to fail when parsing some modules in the unreached-valid.wast test:

type mismatch: br_table target labels have different types (at offset 47)

Expected Behavior

Any compliant WebAssembly parser should be able to successfully parse the spec test modules that are intended to pass (module directives) and fail parsing the spec test modules that are intended to fail (assert_invalid).

Actual Behavior

unreached-valid.wast test fails to parse.