WebKit segfaults when changing to a ConditionalLayout

backtrace from gdb:

#0 0xafbe2e7e in ?? () from /usr/lib/i386-linux-gnu/libQt5WebKit.so.5
#1 0xaf6d8c63 in ?? () from /usr/lib/i386-linux-gnu/libQt5WebKit.so.5
#2 0xaf7fa6b5 in ?? () from /usr/lib/i386-linux-gnu/libQt5WebKit.so.5
#3 0xb7d4b6b9 in QSGNode::destroy() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#4 0xb7d4b6f6 in QSGNode::~QSGNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#5 0xb7d4b7d6 in QSGTransformNode::~QSGTransformNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#6 0xaf7fa620 in ?? () from /usr/lib/i386-linux-gnu/libQt5WebKit.so.5
#7 0xb7d4b6b9 in QSGNode::destroy() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#8 0xb7d4b6f6 in QSGNode::~QSGNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#9 0xb7d4b722 in QSGNode::~QSGNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#10 0xb7d4b6b9 in QSGNode::destroy() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#11 0xb7d4b6f6 in QSGNode::~QSGNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#12 0xb7d4b862 in QSGBasicGeometryNode::~QSGBasicGeometryNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#13 0xb7d4b8d6 in QSGClipNode::~QSGClipNode() ()
---Type <return> to continue, or q <return> to quit---
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#14 0xb7e4d518 in ?? () from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#15 0xb7d4b6b9 in QSGNode::destroy() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#16 0xb7d4b6f6 in QSGNode::~QSGNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#17 0xb7d4b7d6 in QSGTransformNode::~QSGTransformNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#18 0xb7d4b802 in QSGTransformNode::~QSGTransformNode() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#19 0xb7d90603 in QQuickWindowPrivate::cleanupNodes() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#20 0xb7d9065d in QQuickWindowPrivate::updateDirtyNodes() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#21 0xb7d90705 in QQuickWindowPrivate::syncSceneGraph() ()
   from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#22 0xb7e7f482 in ?? () from /usr/lib/i386-linux-gnu/libQt5Quick.so.5
#23 0xb6cbcbb8 in ?? () from /usr/lib/i386-linux-gnu/libQt5Core.so.5
#24 0xb6382d78 in start_thread () from /lib/i386-linux-gnu/libpthread.so.0
#25 0xb6a5d3de in clone () from /lib/i386-linux-gnu/libc.so.6

This seems like the same segfault which happens when you close an app with a not visible WebView.
btw: backtrace with the debugging symbols for qtwebkit:

#0 WebCore::GraphicsLayer::removeAllChildren (this=0x0)
    at platform/graphics/GraphicsLayer.cpp:247
#1 0x00007fffce294f4e in WebKit::LayerTreeRenderer::purgeGLResources (
    this=0x7fffdc070dc0)
    at UIProcess/CoordinatedGraphics/LayerTreeRenderer.cpp:664
#2 0x00007fffce39d907 in ~ContentsSGNode (this=0x7fff7521c690,
    __in_chrg=<optimized out>) at UIProcess/qt/QtWebPageSGNode.cpp:64
#3 WebKit::ContentsSGNode::~ContentsSGNode (this=0x7fff7521c690,
    __in_chrg=<optimized out>) at UIProcess/qt/QtWebPageSGNode.cpp:65
#4 0x00007ffff7998e33 in QSGNode::destroy() ()
   from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#5 0x00007fffce39d863 in ~QtWebPageSGNode (this=0x7fff7521c450,
    __in_chrg=<optimized out>) at UIProcess/qt/QtWebPageSGNode.h:37
#6 WebKit::QtWebPageSGNode::~QtWebPageSGNode (this=0x7fff7521c450,
    __in_chrg=<optimized out>) at UIProcess/qt/QtWebPageSGNode.h:37

Michael, Can you reproduce this error still? The layouting logic has been changed since you submitted the bug, perhaps this got fixed as well.