V7: This dictionary cannot be used anymore, because its content is now owned by an object of a derived class

[TomasMadajevas]

V7-alpha fails with System.InvalidOperationException: 'This dictionary cannot be used anymore, because its content is now owned by an object of a derived class.' when attempting to merge one document into another:

using var source = PdfReader.Open("./with_newline_whitespace_in_indirect_object_numbers.pdf", PdfDocumentOpenMode.Import);
using var destination = new PdfDocument();

foreach (var page in source.Pages)
{
    destination.AddPage(page);
}

File taken from pdf-lib (just found repro, happens with real life files too):
with_newline_whitespace_in_indirect_object_numbers.pdf.

This does work with 6.2.4.