WCoverArtMenu - implements method to show the menu + do not open it when the trackId is invalid
The method show(...) will be responsible to get the position and the other parameters as well.
In this way, callers do not need to call updateData() and exec()...
It is also important that all callers do not use popup() or exec() any more...
WCoverArtMenu - hide showFullSize action when the current cover is the default one