Similarly to #41145, creating and deleting QApplication twice in a GTK environment leads to a segfault:
```
$ gdb python
<elided>
(gdb) run -c 'from PyQt4.QtGui import *; app = QApplication([]); del app; app = QApplication([])'
Starting program: /usr/bin/python -c 'from PyQt4.QtGui import *; app = QApplication([]); del app; app = QApplication([])'
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x00007fffebb3614d in gtk_container_add () from /usr/lib/libgtk-x11-2.0.so.0
(gdb) bt
#0 0x00007fffebb3614d in gtk_container_add ()
from /usr/lib/libgtk-x11-2.0.so.0
#1 0x00007ffff566ae56 in ?? () from /usr/lib/libQtGui.so.4
#2 0x00007ffff566be8e in ?? () from /usr/lib/libQtGui.so.4
#3 0x00007ffff566ed39 in ?? () from /usr/lib/libQtGui.so.4
#4 0x00007ffff5651611 in QGtkStyle::QGtkStyle() () from /usr/lib/libQtGui.so.4
#5 0x00007ffff55d808d in QStyleFactory::create(QString const&) ()
from /usr/lib/libQtGui.so.4
#6 0x00007ffff52ce08e in QApplication::style() () from /usr/lib/libQtGui.so.4
#7 0x00007ffff52ce46d in QApplicationPrivate::initialize() ()
from /usr/lib/libQtGui.so.4
#8 0x00007ffff52ce58a in QApplicationPrivate::construct(_XDisplay*, unsigned long, unsigned long) () from /usr/lib/libQtGui.so.4
#9 0x00007ffff52ce82f in QApplication::QApplication(int&, char**, int) ()
from /usr/lib/libQtGui.so.4
#10 0x00007ffff6349c1e in ?? ()
from /usr/lib/python3.5/site-packages/PyQt4/QtGui.so
#11 0x00007ffff6349e06 in ?? ()
from /usr/lib/python3.5/site-packages/PyQt4/QtGui.so
#12 0x00007ffff12740b3 in ?? () from /usr/lib/python3.5/site-packages/sip.so
#13 0x00007ffff79d1126 in ?? () from /usr/lib/libpython3.5m.so.1.0
#14 0x00007ffff797643a in PyObject_Call () from /usr/lib/libpython3.5m.so.1.0
<elided>
```