Signals without arguments give false warnings in QML in Android

Steps

1. Build and launch any example that has a 0-parameter signal from QML to Java, e.g. qtdeclarative/examples/platforms/android/qtquickview_java
2. Press the button that causes the onClicked() signal to be sent

Expected Result

1. No warnings.

Actual Result

1. libqtquick..._x86_64.so com.example.qtquickview_java         W  Mismatching argument types between QML signal (onClicked()) and the Java function (java/lang/Void). Sending null as argument.

Probable cause

In QAndroidViewSignalManager::invokeListener, where this warning is printed, we don't handle this case correctly. In this case the generated Java/Kotlin code expects the user to supply a QtSignalListener<Void>, which will have a method onSignalEmitted(String, Void). But the C++ side does not recognize that Void can be a type when getting the value for that parameter, and so the variable "jValue" ends up being invalid and that results in this warning.

Probably either the QtSignalListener<Void> has to be replaced with a QtSignalListener without a type parameter, or QAndroidTypeConverter::toJavaObject has to be extended to handle Void types along with adding a Void overload to QAndroidViewSignalManager methods.