Fix crash on closing Words.
The bug was introduced ~2 weeks ago with 2fe68748b069
backtrace;
[KCrash Handler]
6 0x00007fedf9e5b12a in KoInlineObject::d_func (this=0x0) at /home/kdab/src/calligra/libs/kotext/KoInlineObject.h:228
7 0x00007fedf9e5afb6 in KoInlineObject::id (this=0x0) at /home/kdab/src/calligra/libs/kotext/KoInlineObject.cpp:85
8 0x00007fedf9e5284a in KoInlineTextObjectManager::removeInlineObject (this=0x9dd260, object=0x0) at /home/kdab/src/calligra/libs/kotext/KoInlineTextObjectManager.cpp:146
9 0x00007fedf9f178b4 in DeleteCommand::~DeleteCommand (this=0x4852dc0, __in_chrg=<value optimized out>) at /home/kdab/src/calligra/libs/kotext/commands/DeleteCommand.cpp:299
10 0x00007fedf9f17b36 in DeleteCommand::~DeleteCommand (this=0x4852dc0, __in_chrg=<value optimized out>) at /home/kdab/src/calligra/libs/kotext/commands/DeleteCommand.cpp:306
11 0x00007fedf953672c in qDeleteAll<QList<KUndo2Command*>::const_iterator> (begin=..., end=...) at /usr/include/QtCore/qalgorithms.h:322
12 0x00007fedf95361e8 in qDeleteAll<QList<KUndo2Command*> > (c=...) at /usr/include/QtCore/qalgorithms.h:330
13 0x00007fedf95349a1 in KUndo2QStack::clear (this=0x9780a0) at /home/kdab/src/calligra/libs/kundo2/kundo2stack.cpp:521
14 0x00007fedfa4ccfdf in KoDocument::clearUndoHistory (this=0x90dac0) at /home/kdab/src/calligra/libs/main/KoDocument.cpp:2747
15 0x00007fedfa4ebfb0 in KoMainWindow::setRootDocument (this=0x8a5620, doc=0x0) at /home/kdab/src/calligra/libs/main/KoMainWindow.cpp:456
16 0x00007fedfa4efd7a in KoMainWindow::closeEvent (this=0x8a5620, e=0x7fffa36d3340) at /home/kdab/src/calligra/libs/main/KoMainWindow.cpp:1027