Remove mixed flowline types in prepro (#1151)
Remove mixed flowline types in prepro (#1151)


OGGM/oggm,bearecinos/oggm,juliaeis/oggm,juliaeis/oggm,TimoRoth/oggm,anoukvlug/oggm,OGGM/oggm,TimoRoth/oggm,bearecinos/oggm,anoukvlug/oggm