∀ {α : Type u_1} [inst : MeasurableSpace α] {M : Type u_2} [inst_1 : AddCommMonoid M] [inst_2 : TopologicalSpace M]
  (v : MeasureTheory.VectorMeasure α M) (i x : Set α),
  ¬MeasurableSet x → (if MeasurableSet x then ↑v (x ∩ i) else 0) = 0