message: compress: do not leak memory for zero-sized result
  + fix allocation in LLVM mode.
diff: @@ -570,8 +570,13 @@ struct JitArray : ArrayBase<Value_, is_mask_v<Value_>, Derived_> {
  eval_();
  uint32_t size_out = jit_compress(Backend, (const uint8_t *) data(),
  size_in, indices);
  + if (size_out > 0) {
  return int32_array_t<Derived>::steal(
  jit_var_mem_map(Backend, VarType::UInt32, indices, size_out, 1));
  + } else {
  + jit_free(indices);
  + return int32_array_t<Derived>();
  + }
  }
  }
  