CC0013 (user ternary) rule should be more careful with nullable types. (VB)

for example, this:
    If value Is DBNull.Value Then
                    Return Nothing
    Else
                    Return CDate(value)
    End If
not equals to:
Return If(value Is DBNull.Value, Nothing, CDate(value))

first will return Nothing, but second will return DateTime.MinValue.
