bugfixes for GED mode: correctly use mustache conversions, avoid association of ECAL driven electron to wrong SC

Fix the following bugs:
- not checking to merge refineable objects through association by brem tangents (allows tracker driven gsf tracks to pull in super clusters with no associated gsf track)
- fix a bug when in GED mode where the wrong super cluster would get associated to an ECAL driven electron, this was coming from a null seed det ID in the seed PFClusters, which seems like a somewhat deeper bug.

Both of these fixes improve low-side (i.e. below 0.5) tails in the E_reco/E_true distribution for refined superclusters coming from electrons.