[Sys.Data] Add unit tests for Novell bug #519648

These unit tests demonstrate the difference to .NET
(https://bugzilla.novell.com/show_bug.cgi?id=519648).
[Sys.Data] Fix Novell Bug #519648

Don't throw an exception when passing "new object[] {null}" to
DataRowCollection.Find. This makes the behaviour more compatible
with .NET. This fixes bug #519648
(https://bugzilla.novell.com/show_bug.cgi?id=519648).