For an unknown reason, if a download prompt is triple-nested, Qt segfaults here:
#0 add_lazy_attrs (td=0x7ffff52e0dd1 <QtPrivate::sizedFree(void*, unsigned long)+32>) at sip_core.c:6255
#1 sip_add_all_lazy_attrs (td=0x7ffff52e0dd1 <QtPrivate::sizedFree(void*, unsigned long)+32>) at sip_core.c:6304
#2 0x00007ffff636598e in sip_api_is_py_method_12_8 (gil=gil@entry=0x7fffffff8b8c, pymc=pymc@entry=0x7fffffff8b8b "", sipSelfp=sipSelfp@entry=0x7fffffff8ba8, cname=cname@entry=0x0, mname=mname@entry=0x7ffff636d57b "__dtor__") at sip_core.c:7402
#3 0x00007ffff6365c2c in sip_api_is_py_method_12_8 (mname=0x7ffff636d57b "__dtor__", cname=0x0, sipSelfp=0x7fffffff8ba8, pymc=0x7fffffff8b8b "", gil=0x7fffffff8b8c) at sip_core.c:7356
#4 callPyDtor (self=<optimized out>) at sip_core.c:5375
#5 sip_api_instance_destroyed_ex (sipSelfp=0x7fffffff8c40) at sip_core.c:5311
#6 0x00007ffff5fc9967 in sipQEventLoop::~sipQEventLoop() () from [...]/python3.13/site-packages/PyQt6/QtCore.abi3.so
#7 0x00007ffff0bcd749 in QFileInfoGatherer::getInfo (this=0x5555583f9bc0, fileInfo=...) at [...]/qt5/qtbase/src/gui/itemmodels/qfileinfogatherer.cpp:349
#8 0x00007ffff0be2629 in QFileSystemModelPrivate::fileSystemChanged (this=0x5555583f9870, path="/tmp/qbdl/download", updates=QList<std::pair<QString, QFileInfo>> (size = 3) = {...}) at [...]/qt5/qtbase/src/gui/itemmodels/qfilesystemmodel.cpp:1966
(full stacktrace has 183 frames)
After a lot of experimentation, I figured out that moving the `NullIconProvider`
to a class variable (or removing it entirely) seems to help. Note that making it
`global` (but keeping the instanciation inside `FilenamePrompt._init_fileview()`)
did not!
This is semi-blind fix: It's unclear to me if this is a proper fix, or if the
changed memory layout just causes the issue to temporary disappear.
However, given that `QFileInfoGatherer::getInfo()` calls into the icon provider,
it might very well be the real deal.
Closes#8674
c6b486ce81