Empty strings are passed to report_event func

I've built an example of the event_log ("example/event_log").
But it doesn't work.
Instead of
`The drive C: has low free disk space. At least 2097152 Mb of free space is recommended`
I've got
`The drive has low free disk space. At least Mb of free space is recommended.`.

There is an array of empty strings in the report_event call: `
WORD wNumStrings = 2; const char** lpStrings = { "", ""}.
`
Maybe, it is related to:
```cpp
void operator() (record_view const& rec, insertion_list& insertions) const
{
std::size_t size = m_Formatters.size();
insertions.resize(size);
for (std::size_t i = 0; i < size; ++i)
{
typename formatter_type::stream_type strm(insertions[i]);
m_Formatters[i](rec, strm);
strm.flush();
}
}
```
After calling `strm.flush();` `insertions[i]` is empty,