godot: Godot editor crashes when debugging started

Godot version:

Godot 3.1.beta from commit ab8f3d784

OS/device including version:

MacOSX 10.13.6 Android 7.1.2

Issue description:

Sometimes (very often) godot editor crashes when debugging started on my android phone. For example, when some error happens in gd script editor should stop running and show the problem. Actually it shows but immediately crashes.

ERROR: get: FATAL: Index p_index=-1 out of size (size()=27)
   At: ./core/cowdata.h:151.
handle_crash: Program crashed with signal 4
Dumping the backtrace. Please include this when reporting the bug on https://github.com/godotengine/godot/issues
[1] 1   libsystem_platform.dylib            0x00007fff76559f5a _sigtramp + 26
[2] _err_error_exists (in godot.osx.opt.tools.64) + 0
[3] TextEdit::_notificationv(int, bool) (in godot.osx.opt.tools.64) (text_edit.h:43)
[4] Object::notification(int, bool) (in godot.osx.opt.tools.64) (object.cpp:955)
[5] CanvasItem::_update_callback() (in godot.osx.opt.tools.64) (scene_string_names.h:52)
[6] MethodBind0::call(Object*, Variant const**, int, Variant::CallError&) (in godot.osx.opt.tools.64) (variant.h:419)
[7] Object::call(StringName const&, Variant const**, int, Variant::CallError&) (in godot.osx.opt.tools.64) (object.cpp:0)
[8] MessageQueue::_call_function(Object*, StringName const&, Variant const*, int, bool) (in godot.osx.opt.tools.64) (variant.h:421)
[9] MessageQueue::flush() (in godot.osx.opt.tools.64) (message_queue.cpp:305)
[10] SceneTree::iteration(float) (in godot.osx.opt.tools.64) (self_list.h:105)
[11] Main::iteration() (in godot.osx.opt.tools.64) (main.cpp:1861)
[12] OS_OSX::run() (in godot.osx.opt.tools.64) (os_osx.mm:2611)
[13] main (in godot.osx.opt.tools.64) (godot_main_osx.mm:102)
[14] 14  libdyld.dylib                       0x00007fff7624b015 start + 1
[15] 15  ???                                 0x0000000000000004 0x0 + 4
-- END OF BACKTRACE --

Steps to reproduce:

Minimal reproduction project: