#78 object resolution

[Alexander]

There are rare cases, when FileIdentifier object can't be resolved to an array of two strings, but a string only. Then PdfObject.Resolve(BaseObject) returns PdfString instead of PdfArray of two strings. The problem resides in FileIdentifier.cs -> FileIdentifier.Update at the end and can be fixed this way:

if (PdfObject.Resolve(BaseObject) is PdfArray)
{
BaseDataObject[1] = versionID;
if (BaseDataObject[0].Equals(PdfString.Default)) BaseDataObject[0] = versionID;
}

The problematic PDF is attached.