wxGUI: fix wxAssertionError when opening tools from console

[petrasovaa]

Since d657c9a sometimes when a tool is opened from GUI console a wxAssertionError appears:

wx._core
.
wxAssertionError
:
C++ assertion "nNew != dynamicEvents.size()" failed at /home
/wxpy/wxPython-4.2.0/ext/wxWidgets/src/common/event.cpp(1930
) in SearchDynamicEventTable():
The above exception was the direct cause of the following
exception:
SystemError
:
<class 'wx._core.ChildFocusEvent'> returned a result with an
error set

I don't fully understand why that happens, but I don't think there is anything wrong in our code. Writing the hint after the OnKillFocus event is resolved seems to fix the problem.