Fix to always add a Dummy vertex to the FTK VertexContainer
This is a fix for a crash in Jet tools with an empty FTK VertexContainer. ATR-19565 The FTK_DataProviderSvc has been changed to add a dummy vertex in this case. This has been tested with TrigP1test/test_HLT_physics_FTK_build.sh TriggerTest/test_mc_pp_v8_ftk_build.sh