To be fair, I asked, so I could answer, so it would be ready when people come looking.
SpaceX aims at the water, away from the actual landing point (pad, barge, whatever) and only diverts if all is going well.
They thought about this exact circumstance in advance and it worked well. They did not need to divert away as they were not yet aimed at the landing pad.
This can be seen when the Falcon Heavy center core failed to land on the ASDS OCISLY earlier in 2018 it was aimed off to the side, and ran out of fuel to divert to the actual barge surface.