Fix AppearanceData TODO in LayoutFunctions.cpp

[webern]

Fix this TODO

Sourcecode/private/mx/impl/LayoutFunctions.cpp:421

            for( const auto& other : appearance.getOtherAppearanceSet() )
            {
                api::AppearanceData data{};
                data.appearanceType = api::AppearanceType::Distance;
                data.appearanceSubType = core::toString( other->getAttributes()->type );

                // TODO - fix
                data.value = 0.0;//other->getValue().getValue();
                outDefaults.appearance.emplace_back( std::move( data ) );
            }