Godot crash when exiting it

[qarmin]

Godot version:
3.1 cca0ffe

OS/device including version:
Ubuntu 18.04 Nvidia 970 Proprietary

Issue description:
When I exited godot with loaded tps-demo then this backtrace was shown:

[1] /lib/x86_64-linux-gnu/libc.so.6(+0x3ef20) [0x7f8328879f20] (??:0)
[2] Control::get_icon(StringName const&, StringName const&) const (/home/rafal/Pulpit/godot/scene/gui/control.cpp:816 (discriminator 6))
[3] EditorResourcePreview::_generate_preview(Ref<ImageTexture>&, Ref<ImageTexture>&, EditorResourcePreview::QueueItem const&, String const&) (/home/rafal/Pulpit/godot/editor/editor_resource_preview.cpp:158 (discriminator 6))
[4] EditorResourcePreview::_thread() (/home/rafal/Pulpit/godot/editor/editor_resource_preview.cpp:240)
[5] EditorResourcePreview::_thread_func(void*) (/home/rafal/Pulpit/godot/editor/editor_resource_preview.cpp:94)
[6] ThreadPosix::thread_callback(void*) (/home/rafal/Pulpit/godot/drivers/unix/thread_posix.cpp:72)
[7] /lib/x86_64-linux-gnu/libpthread.so.0(+0x76db) [0x7f83297766db] (??:0)
[8] /lib/x86_64-linux-gnu/libc.so.6(clone+0x3f) [0x7f832895c88f] (??:0)