Event wasn't created and ui app crashes

If we try to create new event, using ui, event wasn't created
IGTM, it is because we have a bad callback in button rebinding

 Traceback (most recent call last):
   File "shellper/ui/main.py", line 201, in <module>
     ShellperApp().run()
   File "/usr/local/lib/python2.7/dist-packages/kivy/app.py", line 824, in run
     runTouchApp()
   File "/usr/local/lib/python2.7/dist-packages/kivy/base.py", line 487, in runTouchApp
     EventLoop.window.mainloop()
   File "/usr/local/lib/python2.7/dist-packages/kivy/core/window/window_pygame.py", line 398, in mainloop
     self._mainloop()
   File "/usr/local/lib/python2.7/dist-packages/kivy/core/window/window_pygame.py", line 285, in _mainloop
     EventLoop.idle()
   File "/usr/local/lib/python2.7/dist-packages/kivy/base.py", line 330, in idle
     self.dispatch_input()
   File "/usr/local/lib/python2.7/dist-packages/kivy/base.py", line 315, in dispatch_input
     post_dispatch_input(*pop(0))
   File "/usr/local/lib/python2.7/dist-packages/kivy/base.py", line 221, in post_dispatch_input
     listener.dispatch('on_motion', etype, me)
   File "kivy/_event.pyx", line 699, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7011)
   File "/usr/local/lib/python2.7/dist-packages/kivy/core/window/__init__.py", line 904, in on_motion
     self.dispatch('on_touch_down', me)
   File "kivy/_event.pyx", line 699, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7011)
   File "/usr/local/lib/python2.7/dist-packages/kivy/core/window/__init__.py", line 920, in on_touch_down
     if w.dispatch('on_touch_down', touch):
   File "kivy/_event.pyx", line 699, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7011)
   File "/usr/local/lib/python2.7/dist-packages/kivy/uix/widget.py", line 382, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy/_event.pyx", line 699, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7011)
   File "/usr/local/lib/python2.7/dist-packages/kivy/uix/widget.py", line 382, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy/_event.pyx", line 699, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7011)
   File "/usr/local/lib/python2.7/dist-packages/kivy/uix/widget.py", line 382, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy/_event.pyx", line 699, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7011)
   File "/usr/local/lib/python2.7/dist-packages/kivy/uix/behaviors.py", line 135, in on_touch_down
     self.dispatch('on_press')
   File "kivy/_event.pyx", line 695, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:6970)
   File "kivy/_event.pyx", line 1168, in kivy._event.EventObservers.dispatch (kivy/_event.c:12154)
   File "kivy/_event.pyx", line 1092, in kivy._event.EventObservers._dispatch (kivy/_event.c:11729)
   File "shellper/ui/main.py", line 135, in <lambda>
     on_press=lambda c: self.verify_fields())
   File "shellper/ui/main.py", line 56, in verify_fields
     self.submit_button.bind(on_press=self.callback())
   File "kivy/_event.pyx", line 428, in kivy._event.EventDispatcher.bind (kivy/_event.c:5456)
 AssertionError: <kivy.uix.floatlayout.FloatLayout object at 0x7f93b939dc18> is not callable