'Nomady' adding to '601' above. I think you maybe misguided there with that belief (A/C on rwy has ROW) in this case. The better statement would have been you can't land (unless in an Emerg) on a Rwy already occupied & not by just an A/C either. Obviously the lightie had ROW due his position in the circuit.
Obviously both pilots would not have done this deliberately (well we hope not anyway) so either there was some misunderstanding re where who was or what some intentions where or the Dash simply didn't see the lightie on short final. We don't know the exact details here there could have been sun-glare (if it was daylight I haven't read the report as yet), could have been inadequate R/T proc's.
I'd like to think that the Lightie driver will be more at the ready to go around rather than land if he/she comes across this another time.
We all learn & it's when we stop learning that it becomes very dangerous.
Wmk2