Update InternalBitConverter.cs

[Zombach]

Document metadata streams begin with a unicode character like "\u0005DocumentSummary\0\0\0\0\0\0". In windows, if you call .IndexOf("\0") on that string, it will treat the "\u0005" as a single unmatching character and return the index of the first \0 after DocumentSummary. In Linux, the null byte that is part of the "\u0005" character will get detected and it will delete everything after the initial byte.