[Agda] Bug in the strictly positivity check

[Florent Balestrieri]

I thought records and data definitions should be treated in the same 
way, but the attached program shows Agda makes a difference.

All the best
-- Florent

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module NSP where

record Top : Set where

-- ! NSP is not strictly positive, because it occurs to the left of an
-- ! arrow in the type of the constructor nsp1 in the definition of NSP.

-- data NSP : Set where
--   nsp : ((NSP -> Top) -> Top) -> NSP

record NSP : Set where
  field
    nsp : (NSP -> Top) -> Top