BOOST_FUSION_ADAPT_ADT `not enough actual parameters for macro`

On MSVC if one wants to leave the setter/getter empty, e.g.:
```cpp
BOOST_FUSION_ADAPT_ADT(
data4,
(boost::optional, boost::optional const&, obj.a(), /**/)
(boost::optional, boost::optional const&, obj.b(), /**/)
(boost::optional, boost::optional const&, obj.c(), /**/)
);
```
will get a warning message:
```
..\libs\spirit\test\karma\regression_adapt_adt.cpp(110): warning C4003: not enough actual parameters for macro 'BOOST_PP_SEQ_SIZE_3'
..\libs\spirit\test\karma\regression_adapt_adt.cpp(110): warning C4003: not enough actual parameters for macro 'BOOST_PP_SEQ_ELEM_0'
```
Is it safe to ignore it?
Are there any methods except disabling the warning to fix this? MSVC will compile fine and without the warning if you replace `/**/` with `()` but it does not work for GCC and Clang,