Fix memory leaks

There seem to be some memory leaks on master

==42715== HEAP SUMMARY:
==42715==     in use at exit: 519,608 bytes in 8,063 blocks
==42715==   total heap usage: 367,931 allocs, 359,868 frees, 184,150,309 bytes allocated
==42715== 
==42715== 24 bytes in 1 blocks are definitely lost in loss record 83 of 492
==42715==    at 0x483ADEF: operator new(unsigned long) (vg_replace_malloc.c:342)
==42715==    by 0x14589C: KBlocksScene::createGameItemGroups(int, bool) (KBlocksScene.cpp:91)
==42715==    by 0x14B4D6: KBlocksWin::startGame() (KBlocksWin.cpp:109)
==42715==    by 0x14B55F: KBlocksWin::startGame() (KBlocksWin.cpp:126)
==42715==    by 0x14B894: KBlocksWin::singleGame() (KBlocksWin.cpp:172)
==42715==    by 0x1516BF: KBlocksWin::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (moc_KBlocksWin.cpp:122)
==42715==    by 0x6BCCE0F: ??? (in /usr/lib/libQt5Core.so.5.15.2)
==42715==    by 0x5CD1F62: QAction::triggered(bool) (in /usr/lib/libQt5Widgets.so.5.15.2)
==42715==    by 0x5CD4844: QAction::activate(QAction::ActionEvent) (in /usr/lib/libQt5Widgets.so.5.15.2)
==42715==    by 0x5CD5487: QAction::event(QEvent*) (in /usr/lib/libQt5Widgets.so.5.15.2)
==42715==    by 0x5CD8751: QApplicationPrivate::notify_helper(QObject*, QEvent*) (in /usr/lib/libQt5Widgets.so.5.15.2)
==42715==    by 0x6B95A79: QCoreApplication::notifyInternal2(QObject*, QEvent*) (in /usr/lib/libQt5Core.so.5.15.2)
==42715== 
==42715== 152 bytes in 1 blocks are definitely lost in loss record 331 of 492
==42715==    at 0x483ADEF: operator new(unsigned long) (vg_replace_malloc.c:342)
==42715==    by 0x120CBD: main (main.cpp:348)

@helfferich will you have a look after !5 (merged) is merged or prefer i check them?