How to merge two lists based on object indices?

I want to merge to lists, that don't have positions with overlapping elements:

mylist<-list(1,3,2)
otherlist<-list(NULL,NULL,NULL,4,5,6)

# Desired

list(1,3,2,4,5,6)

# my try:

suppressWarnings(mapply(c, mylist, otherlist) )

Answer should be universal