-fprof-late and HasField leads to invalid json file

{-# LANGUAGE DataKinds #-}
module Main where

import GHC.Records

main = print ()

data Person = Person { name :: String }

instance HasField "fullname" Person String where
  getField = name

ghc Prof.hs -O -fprof-late -prof
./Prof +RTS -pj

Then looking in the json file you can see

{"id": 128, "label": "$fHasFieldSymbol"fullname"PersonList", "module": "Main", "src_loc": "Prof.hs:10:10-42", "is_caf": false}, 

which is not escaped properly.

cc @AndreasK

It seems that the escapeString function needs to be extended in ProfilerReportJson.c.