Dark theme icons broken

Description

The dark theme icons broke KiCad icons load on all applications.

Commits related: kicad/code/kicad@e570b9b5, kicad/code/kicad@405fa183

No functionality was broken.

Putting @craftyjon up here: the folder \usr\share\kicad\resources\ doesn't exist, possible packing error?

KiCad Version

Application: KiCad PCB Editor

Version: 5.99.0-unknown-e570b9b548~101~ubuntu20.04.1, release build

Libraries:
	wxWidgets 3.0.4

Platform: Linux 5.8.0-44-generic x86_64, 64 bit, Little endian, wxGTK, ubuntu, x11

	wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.71.0
	OCC: 7.3.0
	Curl: 7.68.0
	ngspice: 31
	Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:
	KICAD_SCRIPTING=ON
	KICAD_SCRIPTING_MODULES=ON
	KICAD_SCRIPTING_PYTHON3=ON
	KICAD_SCRIPTING_WXPYTHON=ON
	KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
	KICAD_SCRIPTING_ACTION_MENU=ON
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON