Bug 382693

I rebuilt libqapt and muon with -g -O0, here's the stack trace:

```
Thread 1 "muon" received signal SIGSEGV, Segmentation fault.
0x00007ffff7648bed in pkgDepCache::FindPkg (this=0x0, Name="dgit") at /usr/include/apt-pkg/depcache.h:358
358        inline PkgIterator FindPkg(std::string const &Name) {return Cache->FindPkg(Name);};
```

```
#0  0x00007ffff7648bed in pkgDepCache::FindPkg (this=0x0, Name="dgit") at /usr/include/apt-pkg/depcache.h:358
#1  0x00007ffff763fe28 in QApt::Backend::package (this=0xa35d80, name=...)
    at libqapt-3.0.3+p16.04+git20170630.2221/src/backend.cpp:346
#2  0x00007ffff7640e1d in QApt::Backend::search (this=0xa35d80, searchString=...)
    at libqapt-3.0.3+p16.04+git20170630.2221/src/backend.cpp:585
#3  0x000000000043acfa in PackageProxyModel::search (this=0x735980, searchText=...)
    at muon-5.7.0-0+16.04+xenial+build4/src/PackageModel/PackageProxyModel.cpp:71
#4  0x00000000004432b2 in PackageWidget::startSearch (this=0x736030)
    at muon-5.7.0-0+16.04+xenial+build4/src/PackageModel/PackageWidget.cpp:410
#5  0x000000000042a1fa in ManagerWidget::reload (this=0x736030)
    at muon-5.7.0-0+16.04+xenial+build4/src/ManagerWidget.cpp:63
#6  0x00000000004289da in MainWindow::reload (this=0x745000)
    at muon-5.7.0-0+16.04+xenial+build4/src/MainWindow.cpp:370
#7  0x00000000004284ae in MainWindow::transactionStatusChanged (this=0x745000, status=QApt::FinishedStatus)
    at muon-5.7.0-0+16.04+xenial+build4/src/MainWindow.cpp:304
#8  0x000000000045dfac in MainWindow::qt_static_metacall (_o=0x745000, _c=QMetaObject::InvokeMetaMethod, 
    _id=12, _a=0x7fffffffd040)
    at muon-5.7.0-0+16.04+xenial+build4/obj-x86_64-linux-gnu/src/moc_MainWindow.cpp:179
#9  0x00007ffff4edbc19 in QMetaObject::activate (sender=0x1d55a00, signalOffset=<optimized out>, 
    local_signal_index=<optimized out>, argv=<optimized out>) at kernel/qobject.cpp:3766
#10 0x00007ffff7682b9f in QApt::Transaction::statusChanged (this=0x1d55a00, _t1=QApt::FinishedStatus)
    at libqapt-3.0.3+p16.04+git20170630.2221/obj-x86_64-linux-gnu/src/moc_transaction.cpp:539
#11 0x00007ffff7671964 in QApt::Transaction::updateProperty (this=0x1d55a00, type=3, variant=...)
    at libqapt-3.0.3+p16.04+git20170630.2221/src/transaction.cpp:632
#12 0x00007ffff7681d37 in QApt::Transaction::qt_static_metacall (_o=0x1d55a00, 
    _c=QMetaObject::InvokeMetaMethod, _id=24, _a=0x7fffffffd2e0)
    at libqapt-3.0.3+p16.04+git20170630.2221/obj-x86_64-linux-gnu/src/moc_transaction.cpp:286
#13 0x00007ffff4edbc19 in QMetaObject::activate (sender=0x1d72f50, signalOffset=<optimized out>, 
    local_signal_index=<optimized out>, argv=<optimized out>) at kernel/qobject.cpp:3766
#14 0x00007ffff767ee8b in OrgKubuntuQaptworker3TransactionInterface::propertyChanged (this=0x1d72f50, _t1=3, 
    _t2=...)
    at libqapt-3.0.3+p16.04+git20170630.2221/obj-x86_64-linux-gnu/src/transactioninterface_p.moc:372
#15 0x00007ffff767e203 in OrgKubuntuQaptworker3TransactionInterface::qt_static_metacall (_o=0x1d72f50, 
    _c=QMetaObject::InvokeMetaMethod, _id=4, _a=0x7fffffffd4b0)
    at libqapt-3.0.3+p16.04+git20170630.2221/obj-x86_64-linux-gnu/src/transactioninterface_p.moc:188
#16 0x00007ffff767eba9 in OrgKubuntuQaptworker3TransactionInterface::qt_metacall (this=0x1d72f50, 
    _c=QMetaObject::InvokeMetaMethod, _id=4, _a=0x7fffffffd4b0)
    at libqapt-3.0.3+p16.04+git20170630.2221/obj-x86_64-linux-gnu/src/transactioninterface_p.moc:313
#17 0x00007ffff383aee3 in QDBusConnectionPrivate::deliverCall (this=<optimized out>, object=<optimized out>, 
    msg=..., metaTypes=..., slotIdx=<optimized out>) at qdbusintegrator.cpp:998
#18 0x00007ffff4edcc59 in QObject::event (this=0x1d72f50, e=<optimized out>) at kernel/qobject.cpp:1246
#19 0x00007ffff58173fc in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x1d72f50, 
    e=0x7fffd8029aa0) at kernel/qapplication.cpp:3717
#20 0x00007ffff581ee07 in QApplication::notify (this=0x7fffffffdb70, receiver=0x1d72f50, e=0x7fffd8029aa0)
    at kernel/qapplication.cpp:3476
#21 0x00007ffff4eaf798 in QCoreApplication::notifyInternal2 (receiver=0x1d72f50, 
    event=event@entry=0x7fffd8029aa0) at kernel/qcoreapplication.cpp:1018
#22 0x00007ffff4eb1f7b in QCoreApplication::sendEvent (event=0x7fffd8029aa0, receiver=<optimized out>)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:233
#23 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0, 
    data=0x69fd60) at kernel/qcoreapplication.cpp:1678
#24 0x00007ffff4eb23e8 in QCoreApplication::sendPostedEvents (receiver=receiver@entry=0x0, 
    event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1532
#25 0x00007ffff4f05323 in postEventSourceDispatch (s=0x6e9ce0) at kernel/qeventdispatcher_glib.cpp:276
#26 0x00007fffeff8f197 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#27 0x00007fffeff8f3f0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#28 0x00007fffeff8f49c in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#29 0x00007ffff4f0492f in QEventDispatcherGlib::processEvents (this=0x6e05e0, flags=...)
    at kernel/qeventdispatcher_glib.cpp:423
#30 0x00007ffff4ead7ca in QEventLoop::exec (this=this@entry=0x7fffffffda70, flags=..., flags@entry=...)
    at kernel/qeventloop.cpp:212
#31 0x00007ffff4eb6704 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1291
#32 0x00000000004261b5 in main (argc=1, argv=0x7fffffffdcb8)
    at muon-5.7.0-0+16.04+xenial+build4/src/main.cpp:62
```

Your apt is broken it fails to open the depcache. Why it doesn't report so during initialization is anyone's guess. Nothing much we can do about this.

Muon is no longer maintained, please switch no a supported alternative like https://apps.kde.org/discover/ or the package manager native no your system.

Sorry for the inconvenience.