message: relax ek.Loop conditions
diff: @@ -419,7 +419,7 @@ def read_indices(*args):
  for i in range(len(a)):
  result.extend(read_indices(a.entry_ref_(i)))
  elif a.IsDiff:
  - if enoki.grad_enabled(a):
  + if enoki.grad_enabled(a) and enoki.flag(enoki.JitFlag.LoopRecord):
  raise enoki.Exception(
  'Symbolic loop encountered a differentiable array '
  'with enabled gradients! This is not supported.')
  @@ -445,7 +445,7 @@ def write_indices(indices, *args):
  for i in range(len(a)):
  write_indices(indices, a.entry_ref_(i))
  elif a.IsDiff:
  - if enoki.grad_enabled(a):
  + if enoki.grad_enabled(a) and enoki.flag(enoki.JitFlag.LoopRecord):
  raise enoki.Exception(
  'Symbolic loop encountered a differentiable array '
  'with enabled gradients! This is not supported.')
  