Kivy can crash when a TextInput.is_focusable is set to False and focus is switched to another widget at same time

[Bakterija]

• Python: All
• OS: Ubuntu 16.04
• Kivy: 1.10 and 1.10.1-dev0
• Kivy installation method: pip

Tested with this test app

Error log:

[INFO   ] [Logger      ] Record log in /home/atis/.kivy/logs/kivy_17-06-26_71.txt
[INFO   ] [Kivy        ] v1.10.1.dev0, git-f91378d, 20170626
[INFO   ] [Python      ] v2.7.12 (default, Nov 19 2016, 06:48:10) 
[GCC 5.4.0 20160609]
[INFO   ] [Factory     ] 194 symbols loaded
[INFO   ] [Image       ] Providers: img_tex, img_dds, img_sdl2, img_pil, img_gif (img_ffpyplayer ignored)
[INFO   ] [OSC         ] using <multiprocessing> for socket
[INFO   ] [Window      ] Provider: sdl2(['window_egl_rpi'] ignored)
[INFO   ] [GL          ] Using the "OpenGL" graphics system
[INFO   ] [GL          ] Backend used <gl>
[INFO   ] [GL          ] OpenGL version <3.0 Mesa 12.0.6>
[INFO   ] [GL          ] OpenGL vendor <Intel Open Source Technology Center>
[INFO   ] [GL          ] OpenGL renderer <Mesa DRI Intel(R) HD Graphics 520 (Skylake GT2) >
[INFO   ] [GL          ] OpenGL parsed version: 3, 0
[INFO   ] [GL          ] Shading version <1.30>
[INFO   ] [GL          ] Texture max size <8192>
[INFO   ] [GL          ] Texture max units <32>
[INFO   ] [Window      ] auto add sdl2 input provider
[INFO   ] [Window      ] virtual keyboard not allowed, single mode, not docked
[INFO   ] [Text        ] Provider: sdl2
[INFO   ] [Clipboard   ] Provider: gtk3(['clipboard_dbusklipper'] ignored)
xclip version 0.12
Copyright (C) 2001-2008 Kim Saunders et al.
Distributed under the terms of the GNU GPL
[INFO   ] [Cutbuffer   ] Provider: xclip
[INFO   ] [CutBuffer   ] cut buffer support enabled
[INFO   ] [GL          ] NPOT texture support is available
[INFO   ] [Base        ] Start application main loop
('NEW FOCUS', 1)
('NEW FOCUS', 2)
('NEW FOCUS', 3)
('NEW FOCUS', 0)
('NEW FOCUS', 1)
('NEW FOCUS', 2)
('NEW FOCUS', 3)
('NEW FOCUS', 0)
[INFO   ] [Base        ] Leaving application in progress...
 Traceback (most recent call last):
   File "<string>", line 140, in <module>
   File "/home/atis/.local/lib/python2.7/site-packages/kivy/base.py", line 502, in runTouchApp
     EventLoop.window.mainloop()
   File "/home/atis/.local/lib/python2.7/site-packages/kivy/core/window/window_sdl2.py", line 663, in mainloop
     self._mainloop()
   File "/home/atis/.local/lib/python2.7/site-packages/kivy/core/window/window_sdl2.py", line 405, in _mainloop
     EventLoop.idle()
   File "/home/atis/.local/lib/python2.7/site-packages/kivy/base.py", line 337, in idle
     Clock.tick()
   File "/home/atis/.local/lib/python2.7/site-packages/kivy/clock.py", line 581, in tick
     self._process_events()
   File "kivy/_clock.pyx", line 367, in kivy._clock.CyClockBase._process_events (/tmp/pip-NNmYND-build/kivy/_clock.c:7700)
   File "kivy/_clock.pyx", line 397, in kivy._clock.CyClockBase._process_events (/tmp/pip-NNmYND-build/kivy/_clock.c:7577)
   File "kivy/_clock.pyx", line 395, in kivy._clock.CyClockBase._process_events (/tmp/pip-NNmYND-build/kivy/_clock.c:7498)
   File "kivy/_clock.pyx", line 167, in kivy._clock.ClockEvent.tick (/tmp/pip-NNmYND-build/kivy/_clock.c:3490)
   File "<string>", line 97, in do_test
   File "kivy/weakproxy.pyx", line 33, in kivy.weakproxy.WeakProxy.__setattr__ (/tmp/pip-NNmYND-build/kivy/weakproxy.c:1471)
   File "kivy/properties.pyx", line 478, in kivy.properties.Property.__set__ (/tmp/pip-NNmYND-build/kivy/properties.c:5572)
   File "kivy/properties.pyx", line 516, in kivy.properties.Property.set (/tmp/pip-NNmYND-build/kivy/properties.c:6405)
   File "kivy/properties.pyx", line 571, in kivy.properties.Property.dispatch (/tmp/pip-NNmYND-build/kivy/properties.c:7105)
   File "kivy/_event.pyx", line 1225, in kivy._event.EventObservers.dispatch (/tmp/pip-NNmYND-build/kivy/_event.c:14035)
   File "kivy/_event.pyx", line 1131, in kivy._event.EventObservers._dispatch (/tmp/pip-NNmYND-build/kivy/_event.c:13193)
   File "/home/atis/.local/lib/python2.7/site-packages/kivy/uix/behaviors/focus.py", line 384, in _on_focus
     self._bind_keyboard()
   File "/home/atis/.local/lib/python2.7/site-packages/kivy/uix/behaviors/focus.py", line 406, in _bind_keyboard
     old_focus = keyboards[keyboard]  # keyboard should be in dict
 KeyError: <kivy.core.window.Keyboard object at 0x7f5a2a459b40>

[Bakterija]

I was testing modification in the pr and it seemed to work properly in this example and my other keyboard heavy apps.