Crash when removing Texture sourceItem

Tested with latest qt5 (7a5069e9) + qtquick3d (aed7f853) dev branches on windows.

Steps:
1) Start tests\manual\sourceItem
2) Press "Destroy sourceItem"
-> Crash with following debug log:

1 rtData qrhid3d11.cpp 1681 0x7ffa02f62166
2 QRhiD3D11::executeCommandBuffer qrhid3d11.cpp 2409 0x7ffa02f5fbe0
3 QRhiD3D11::endFrame qrhid3d11.cpp 1102 0x7ffa02f57078
4 QRhi::endFrame qrhi.cpp 5801 0x7ffa02eca0d0
5 QSGRenderThread::syncAndRender qsgthreadedrenderloop.cpp 810 0x7ffa01ae16ef
6 QSGRenderThread::run qsgthreadedrenderloop.cpp 978 0x7ffa01ae049b
7 QThreadPrivate::start qthread_win.cpp 328 0x7ffa0d9be881
8 BaseThreadInitThunk KERNEL32 0x7ffa9d346fd4
9 RtlUserThreadStart ntdll 0x7ffa9d73cec1

Note: If first toggling "Animate quick content" on & off, then pressing "Destroy" it doesn't crash.