When a MainWindow is closed which starts the exit of the application then it will not get its destructor called and it will have an error in the console

application.wasm:1 Uncaught RuntimeError: invalid index into function table
    at http://localhost:6931/application.wasm:wasm-function[16073]:0x6b7932
    at http://localhost:6931/application.wasm:wasm-function[16152]:0x6c05ed
    at dynCall_vii (http://localhost:6931/application.wasm:wasm-function[18748]:0x79c30a)
    at eval (eval at completeLoadEmscriptenModule (http://localhost:6931/qtloader.js:443:14), <anonymous>:1:225884)
    at IDBRequest.req.onsuccess (eval at completeLoadEmscriptenModule (http://localhost:6931/qtloader.js:443:14), <anonymous>:1:225365)