Merge #16348: qt: Assert QMetaObject::invokeMethod result

64fee48944 qt: Assert QMetaObject::invokeMethod result (João Barbosa)
f27bd96b5f gui: Fix missing qRegisterMetaType(WalletModel*) (João Barbosa)

Pull request description:

  Invalid/wrong dynamic calls aren't verified by the compiler. This PR asserts those dynamic calls. Once we bump Qt to at least 5.10 these can be refactored to use the `invokeMethod` overload that allows connecting to lambdas or member pointers, which are compile checked.

  For reference, one of the overloaded versions is https://doc.qt.io/qt-5/qmetaobject.html#invokeMethod-5.

ACKs for top commit:
  laanwj:
    ACK 64fee48944

Tree-SHA512: d332e5d7eb2c7be5d3fe90e2e4ff20a67800b9664f6637c122a23647a964f7915703d3f086e2de440f695cfe14de268ff581d0092b7736e911952a4f4d248e25

src/qt/bitcoingui.cpp

@@ -1375,12 +1375,13 @@ static bool ThreadSafeMessageBox(BitcoinGUI* gui, const std::string& message, co
     style &= ~CClientUIInterface::SECURE;
     bool ret = false;
     // In case of modal message, use blocking connection to wait for user to click a button
-    QMetaObject::invokeMethod(gui, "message",
+    bool invoked = QMetaObject::invokeMethod(gui, "message",
                                modal ? GUIUtil::blockingGUIThreadConnection() : Qt::QueuedConnection,
                                Q_ARG(QString, QString::fromStdString(caption)),
                                Q_ARG(QString, QString::fromStdString(message)),
                                Q_ARG(unsigned int, style),
                                Q_ARG(bool*, &ret));
+    assert(invoked);
     return ret;
 }