Warning about implicit fallthrough when building Umbrello

[Robert Hairgrove]

In the file associationline.cpp there is a warning issued:

void AssociationLine::reconstructSymbols()
{
     switch( m_associationWidget->associationType() ) {
         case Uml::AssociationType::Exception:
             setLayout(Uml::LayoutType::Polyline); // <<< warning here 
about implicit fallthrough
         case Uml::AssociationType::State:
         case Uml::AssociationType::Activity:
         case Uml::AssociationType::UniAssociation:
         case Uml::AssociationType::Dependency:
             setStartSymbol(Symbol::None);
             setEndSymbol(Symbol::OpenArrow);
             removeSubsetSymbol();
             removeCollaborationLine();
             break;
etc.

I suppose this is a harmless warning, in which case it would be nice if 
it could be turned off?