function pointers call lacks a `DataField` access

[ringabout]

ref #1536

nimcache/str7oj7yj1.c: In function ‘atEnd_0_str7oj7yj1’:
nimcache/str7oj7yj1.c:709:83: error: ‘X60Qt_0_IArefSX53treamX4fbj0str7oj7yj1_str7oj7yj1’ {aka ‘struct X60Qt_0_IArefSX53treamX4fbj0str7oj7yj1_str7oj7yj1’} has no member named ‘atEndImpl_0_str7oj7yj1’
  709 |   X60Qt_0_IAtupleSX45rrorX43ode0sysvq0aslAbool_str7oj7yj1 X60QcanRaise_0 = (*s_13).atEndImpl_0_str7oj7yj1(s_13);
      |       

[ringabout]

Minimized:

type
  Obj = object of RootObj
    id: proc (x: int)

  ObjRef = ref Obj

proc foo(x: ObjRef)  =
  x.id(21)

proc fooCallback(x: int) =
  echo x

var obj = ObjRef(id: fooCallback)

foo(obj)

nimcache/tesp2cp0i1.c:449:10: error: no member named 'id_0_tesp2cp0i1' in 'struct X60Qt_0_IArefSX4fbj0tesp2cp0i1_tesp2cp0i1'
  449 |   (*x_1).id_0_tesp2cp0i1(IL64(21));}
      |   ~~~~~~ ^
1 error generated.