This means we skip the i++ at the end of the loop body.  Maybe that makes sense.
But it means an empty entry in the list doesn't contribute to the count of entries in the group, so you can't use empty entries in file_buffer's list of hosts as a way to "pad" a group you want smaller than usual, e.g. `serf,slave,,chief,minion,underling,hireling,boss` with a groupsize of 4 and ',' as separator doesn't make chief the group leader of serf and slave (a reduced-size group), it makes minion the group leader of all three; and the later entries don't form a complete group.
I'm not familiar enough with what this is for to know whether that's good or bad ...