QPdfDocument::close leaks a handle to the loaded file

Calling QPdfDocument::close leaves a dangling handle to the loaded file.

The following snippet should be able to remove the PDF, but Windows returns a sharing violation error (error code 32), triggering the assert.

    QPdfDocument doc(&a);
    doc.load(R"(Attachment.pdf)");
    doc.close();

    std::error_code errc;
    std::filesystem::remove(R"(Attachment.pdf)", errc);
    assert(errc.value() == 0);