I was just replacing a line h << "blabla " in the middle of a .cpp file with something else.

ASSERT: "line >= startLine()" in file /home/jtorres/kdesrc/frameworks/ktexteditor/src/buffer/katetextblock.cpp, line 56

[KCrash Handler]
#6  0x00007efc12dbd08b in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#7  0x00007efc12da64e9 in __GI_abort () at abort.c:79
#8  0x00007efc1370d9ad in qt_message_fatal (context=..., message=<synthetic pointer>...) at global/qlogging.cpp:1842
#9  0x00007efc1370d9ad in QMessageLogger::fatal(char const*, ...) const (this=this@entry=0x7ffc8c4b2450, msg=msg@entry=0x7efc139afeb0 "ASSERT: \"%s\" in file %s, line %d") at global/qlogging.cpp:880
#10 0x00007efc1370ce2d in qt_assert(char const*, char const*, int) (assertion=<optimized out>, file=<optimized out>, line=<optimized out>) at ../../include/QtCore/../../src/corelib/global/qlogging.h:91
#11 0x00007efc15e320e6 in Kate::TextBlock::line(int) const (this=0x11d1b000, line=22) at /home/jtorres/kdesrc/frameworks/ktexteditor/src/buffer/katetextblock.cpp:56
#12 0x00007efc15e29bf1 in Kate::TextBuffer::line(int) const (this=0x111f2170, line=22) at /home/jtorres/kdesrc/frameworks/ktexteditor/src/buffer/katetextbuffer.cpp:168
#13 0x00007efc15ec1c52 in KateBuffer::plainLine(int) (this=0x111f2170, lineno=22) at /home/jtorres/kdesrc/frameworks/ktexteditor/src/document/katebuffer.h:168
#14 0x00007efc15ea471e in KTextEditor::DocumentPrivate::totalCharacters() const (this=0xffe2010) at /home/jtorres/kdesrc/frameworks/ktexteditor/src/document/katedocument.cpp:912
#15 0x00007efc15e7fe46 in KateWordCompletionModel::shouldStartCompletion(KTextEditor::View*, QString const&, bool, KTextEditor::Cursor const&) (this=0x266fc20, view=0x11befc50, insertedText=..., userInsertion=true, position=...) at /home/jtorres/kdesrc/frameworks/ktexteditor/src/completion/katewordcompletion.cpp:159
#16 0x00007efc15e45b8c in _shouldStartCompletion(KTextEditor::CodeCompletionModel*, KTextEditor::View*, QString, bool, KTextEditor::Cursor const&) (model=0x266fc20, view=0x11befc50, m_automaticInvocationLine=..., m_lastInsertionByUser=true, cursor=...) at /home/jtorres/kdesrc/frameworks/ktexteditor/src/completion/katecompletionwidget.cpp:95
#17 0x00007efc15e4c5f7 in KateCompletionWidget::automaticInvocation() (this=0x12f21e40) at /home/jtorres/kdesrc/frameworks/ktexteditor/src/completion/katecompletionwidget.cpp:1432
#18 0x00007efc1607b945 in KateCompletionWidget::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (_o=0x12f21e40, _c=QMetaObject::InvokeMetaMethod, _id=7, _a=0x7ffc8c4b2810) at /home/jtorres/kdesrc/build/frameworks/ktexteditor/src/KF5TextEditor_autogen/23UEYSZXD4/moc_katecompletionwidget.cpp:185
#19 0x00007efc1392060b in QMetaObject::activate(QObject*, int, int, void**) (sender=0x134c6780, signalOffset=<optimized out>, local_signal_index=0, argv=0x7ffc8c4b2810) at kernel/qobject.cpp:3771
#20 0x00007efc13920c27 in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) (sender=<optimized out>, m=m@entry=0x7efc13b7cd80 <QTimer::staticMetaObject>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x7ffc8c4b2810) at kernel/qobject.cpp:3633
#21 0x00007efc1392c337 in QTimer::timeout(QTimer::QPrivateSignal) (this=<optimized out>, _t1=...) at .moc/moc_qtimer.cpp:200
#22 0x00007efc13920e7b in QObject::event(QEvent*) (this=0x134c6780, e=<optimized out>) at kernel/qobject.cpp:1232
#23 0x00007efc142974b1 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib64/libQt5Widgets.so.5
#24 0x00007efc1429eb00 in QApplication::notify(QObject*, QEvent*) () at /usr/lib64/libQt5Widgets.so.5
#25 0x00007efc138f73c9 in QCoreApplication::notifyInternal2(QObject*, QEvent*) (receiver=0x134c6780, event=0x7ffc8c4b2ae0) at ../../include/QtCore/5.11.1/QtCore/private/../../../../../src/corelib/thread/qthread_p.h:307
#26 0x00007efc139484b8 in QCoreApplication::sendEvent(QObject*, QEvent*) (event=0x7ffc8c4b2ae0, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:234
#27 0x00007efc139484b8 in QTimerInfoList::activateTimers() (this=0x1f6a940) at kernel/qtimerinfo_unix.cpp:643
#28 0x00007efc1394666c in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=<optimized out>, flags=...) at kernel/qeventdispatcher_unix.cpp:514
#29 0x00007efbf9ea52dd in  () at /usr/lib64/libQt5XcbQpa.so.5
#30 0x00007efc138f609b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7ffc8c4b2c90, flags=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#31 0x00007efc138fe212 in QCoreApplication::exec() () at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#32 0x000000000040cd22 in main(int, char**) (argc=<optimized out>, argv=<optimized out>) at /home/jtorres/kdesrc/extragear/kdevelop/kdevelop/app/main.cpp:823