Steps to reproduce:

1) cherry-pick https://gerrit.libreoffice.org/c/core/+/168685 onto current master (as of a4a2cfa1bf746a4c1d379757c99d35ef5ac42cd3 in my case) and build
2) start Writer
3) right-click onto paragraph, select "Paragraph" -> "Paragraph" in context menu.

-> this warning shows:

warn:vcl.builder:332290:332290:vcl/source/window/builder.cxx:3957: unknown class: with-icons

And LO crashes. For me, crashes with qt6 just the same.

Not sure whether the crash is due to that, though, as the Ctrl+K Hyperlink dialog also triggers that warning, but doesn't crash (and shows icons).

Backtrace:


> 1   SvxExtParagraphTabPage::Reset                                       paragrph.cxx         1928 0x7fff59533eea 
> 2   SfxTabDialogController::CreatePages                                 tabdlg.cxx           946  0x7ffff3bf94a1 
> 3   SfxTabDialogController::Start_Impl                                  tabdlg.cxx           1019 0x7ffff3bfa2f9 
> 4   SfxTabDialogController::runAsync                                    tabdlg.cxx           1070 0x7ffff3bfa6de 
> 5   AbstractTabController_Impl::StartExecuteAsync                       swdlgfact.cxx        433  0x7fff59ad9d75 
> 6   VclAbstractDialog::StartExecuteAsync                                abstdlg.hxx          79   0x7fff821b84f4 
> 7   SwTextShell::Execute                                                textsh1.cxx          1639 0x7fff83ab0fd3 
> 8   SfxStubSwTextShellExecute                                           swslots.hxx          3191 0x7fff83aa19b5 
> 9   SfxDispatcher::Call_Impl                                            dispatch.cxx         254  0x7ffff39d699a 
> 10  SfxDispatcher::PostMsgHandler                                       dispatch.cxx         995  0x7ffff39dc886 
> 11  SfxHintPoster::DoEvent_Impl                                         hintpost.cxx         74   0x7ffff3f2ec1e 
> 12  SfxHintPoster::LinkStubDoEvent_Impl                                 hintpost.cxx         54   0x7ffff3f2eb4d 
> 13  Link<void *, void>::Call                                            link.hxx             111  0x7fffee16b6a8 
> 14  ImplHandleUserEvent                                                 winproc.cxx          2285 0x7fffee167349 
> 15  ImplWindowFrameProc                                                 winproc.cxx          2849 0x7fffee163d00 
> 16  SalFrame::CallCallback                                              salframe.hxx         312  0x7fffe4056fe0 
> 17  QtInstance::ProcessEvent                                            QtInstance.cxx       518  0x7fffe407a65f 
> 18  SalUserEventList::DispatchUserEvents(bool)::$_0::operator()() const salusereventlist.cxx 119  0x7fffee902c5d 
> 19  SalUserEventList::DispatchUserEvents                                salusereventlist.cxx 120  0x7fffee902b04 
> 20  QtInstance::ImplYield                                               QtInstance.cxx       444  0x7fffe4076d51 
> ... <More>                                                                                                       

Relevant line from frame 1:

    m_xAcrossText->set_sensitive(bEnable);

where `m_xAcrossText` is null. Ctor has this:

    , m_xAcrossText(m_xBuilder->weld_label(u"labelHyphenAcross"_ustr))

Could the crash maybe due to some other issue with the UI element with ID `labelHyphenAcross`?

(In reply to Michael Weghorn from comment #1)
> warn:vcl.builder:332290:332290:vcl/source/window/builder.cxx:3957: unknown
> class: with-icons

This does not seem to be the reason for the crash indeed. This is just a warning that happens to take place right before the crash.

> Could the crash maybe due to some other issue with the UI element with ID
> `labelHyphenAcross`?

I commented out "m_xAcrossText->set_sensitive(bEnable);" and the dialog stops crashing.

Now I'm just wondering why the crash happens only with Heiko's patch applied. When the patch is applied, I get the crash. I'd say the issue is with the changes in textflowpage.ui. The conversion Glade made may have broken something. If you compare the new .ui file, it's very different.

Was caused by the attempt to disable the label of an expander rather than the actual control.