Point editor handles are invisible against a white background

Description

When selecting a single sub-sheet in eeschema the (default blue) highlight has white or blank corners. If you select multiple via ctrl+click or block drag selection they all render fine.

Steps to reproduce

1. Select a single sub-sheet
2. Observer corners

KiCad Version

Application: Eeschema
Version: (5.99.0-2197-g5d5706b8b), debug build
Libraries:
	wxWidgets 3.0.5
Platform: Linux 5.6.15-arch1-1 x86_64, 64 bit, Little endian, wxGTK
	wxWidgets: 3.0.5 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
	Boost: 1.72.0
	OCC: 7.4.0
	Curl: 7.70.0
	Compiler: GCC 10.1.0 with C++ ABI 1014

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=OFF
	KICAD_STDLIB_DEBUG=OFF
	KICAD_STDLIB_LIGHT_DEBUG=OFF
	KICAD_SANITIZE=OFF