Use QGuiApplication instead of QCoreApplication to avoid runtime warning "Cannot use KWindowSystem without a QGuiApplication"
Provide argc and argv for QGuiApplication object as its documentation requires:
"The data referred to by argc and argv must stay valid for the entire lifetime of the QGuiApplication object. In addition, argc must be greater than zero and argv must contain at least one valid character string."

set kwallet as credential provider
connected account with saved credentials
disconnected credential provider externally
created and connected new account and saved credentials
restarted pidgin to let accounts autoconnect