Definitely no contact.
it was an excellent ride by Thompson to work his way under Kerr off the second bend - he had tried it the previous lap and obviously thought if he got it right it would work, and it did. Unfortunately, he then made entirely the wrong choice entering the first bend on the final lap - I wonder if the track had got Thompson confused, and he thought he'd be better off trying to put his back wheel on the grippy line, instead of trusting the inside that had served him so well? As it is, Kerr saw a big gap, took advantage, and Thompson had nowhere to go on the outside, which offered nothing at all.
The Ref would have had a clear view.
When offered such a gap, any rider would have done what Kerr did - if it had been an Witch inside a Star, I'm sure the fans would have been miffed if the Witch had been excluded.
Overall, the Witches should never have been in the position of needing three 5-1s in the last three heats at home! KL did just about everything right - and earned a (cough) well-deserved aggregate victory.