Double Dispose() of ZipWritingStream

[aienabled]

Hello!

I've noticed that ZipWritingStream on Dispose method call will produce a new ZipEntry.
But it doesn't have protection against subsequent Dispose call. For example:

using (var stream = zipWriter.WriteToStream(FileNameHeader, new ZipWriterEntryOptions()))
using (var streamWriter = new StreamWriter(stream))
{
   ...
}

it will call dispose for ZipWritingStream two times and produce two zip entries in the archive.
I didn't checked it for other streams (non-zip) but they also could be affected by this issue.

Regards!

[adamhathcock]

Good find. Any chance for a pull request? :)

[aienabled]

Sure #295

[adamhathcock]

Thanks!