Replay dropoff graphic bug


Dropoffs can show (or not show) incorrectly in the online replay viewer.

Steps to reproduce:
-Pause replay
-Go to the turn a dropoff is created.
-Rewind or step back.
-Note that the dropoff is shown before it was created.

There is also the (presumably related) reverse scenario:
-Advance replay past point a dropoff is created.
-Step back to the turn just before it was created.
-Advance or play.
-Note that the dropoff is not shown after being created.