Change to new connect-Syntax
From https://doc.qt.io/qt-5/signalsandslots.html
There are several advantages to using QObject::connect() with function pointers. First, it allows the compiler to check that the signal's arguments are compatible with the slot's arguments. Arguments can also be implicitly converted by the compiler, if needed.
Especially the compile-time check instead of runtime check, whether the connection is possible is a very nice to have feature. This can help during refactorings which could break existing connections due to a change in the function arguments of a slot.