n d = (k + 1/2) λ / 2 the optical thickness of the film is and odd number of 1/4 λ for destructive interference
where n for the lens > n for film so there is a phase change at both surfaces
If k = 1 then n d = λ / 4
Let L be the optical path at ˜ 45 deg
Then L sin 45 = 2 n d = λ / 2 for the total path length thru the film
So L = .7 λ and there would only partial interference
Suppose the total path length were 3.5 λ (destructive interference) then L = 4.95 λ
which would give constructive interference.
It's probably difficult to get a film of only λ / 4 thickness so the answer would depend on the actual thickness of the film
so in general one would not expect to get destructive interference except for particular film thicknesses.
(Suppose the direct path length thru the film is 14.5 λ then L ˜ 20.5 λ and you get cancellation)