pcbnew: DRC Control violations list scrolling resets to top when returning focus to pcbnew

Description

when scrolled down in the list of DRC violations, upon switching focus to pcbnew, the list scrolling resets to the top
2020-08-01T11_22_13+02_00

Steps to reproduce

1. run DRC check in pcbnew that yields enough violations/markers to require scrolling
   1.1. e.g.: https://gitlab.com/evils/waad/-/tree/master/pcb
2. scroll down in the violations list
3. click the canvas in pcbnew
4. see the scroll bar returned to the top in the DRC Control window

Notes

i'm on sway using xwayland with multiple monitors
it seems like any change in focus to or from the DRC Control window causes it to reset the scroll point

KiCad Version

Application: Pcbnew

Version: 5.99.0-9977299340-1, debug build

Libraries:
	wxWidgets 3.1.3
	libcurl/7.71.1 OpenSSL/1.1.1g zlib/1.2.11 libssh2/1.9.0 nghttp2/1.40.0

Platform: Linux 5.7.0-rc4 x86_64, 64 bit, Little endian, wxGTK

Build Info:
	Date: Jan  1 1970 00:00:01
	wxWidgets: 3.1.3 (wchar_t,wx containers) GTK+ 3.24
	Boost: 1.69.0
	OCC: 7.3.0
	Curl: 7.71.1
	ngspice: 31
	Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:
	KICAD_SCRIPTING=OFF
	KICAD_SCRIPTING_MODULES=OFF
	KICAD_SCRIPTING_PYTHON3=OFF
	KICAD_SCRIPTING_WXPYTHON=OFF
	KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
	KICAD_SCRIPTING_ACTION_MENU=OFF
	BUILD_GITHUB_PLUGIN=ON
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON
	KICAD_STDLIB_DEBUG=ON
	KICAD_SANITIZE=OFF