WASM toolbar menu closing sequence causes null function or function signature mismatch

While checking for QTBUG-102802, this issue emerged. 

To reproduce the issue, the same application is used as in 102802. The only difference is that it was compiled with the latest Qt (from repo, 2022-04-25) and using Emscripten version 3.1.6.

Precompiled version is available here: https://nagyimre.com/testwasm_316

Method to reproduce:

Open application in a webbrowser. Open Thread menu, then click the upper white area containing "arg[0]=..." line. This closes the menu. Repeat this in a normal speed and in 3-10 attempts, the attached error would occur.