PCBNew - Import settings from another board deleted all routing from internal layers.

Description

Not sure how exactly this happened but after doing import settings in board setup from a two layer board to a four layer board and checking all the boxes there I ended up with all the routing on the internal layers missing. The layers are still there, they are just blank. That doesn't seem like a smart thing to do when you think that you are just importing "settings"

Steps to reproduce

1. Open an existing 2 layer design and do Board Setup -> Default Tracks and Vias -> Import settings from another board and select all the options there
2. Check your internal layer routing.

KiCad Version

Application: KiCad

Version: (5.99.0-2306-g9f20c61fa), release build

Libraries:
	wxWidgets 3.0.4

Platform: Windows 8 (build 9200), 64-bit edition, 64 bit, Little endian, wxMSW

	wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8)
	Boost: 1.71.0
	OCE: 6.9.1
	Curl: 7.66.0
	ngspice: 31
	Compiler: GCC 9.2.0 with C++ ABI 1013

Build settings:
	KICAD_SCRIPTING=ON
	KICAD_SCRIPTING_MODULES=ON
	KICAD_SCRIPTING_PYTHON3=OFF
	KICAD_SCRIPTING_WXPYTHON=ON
	KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
	KICAD_SCRIPTING_ACTION_MENU=ON
	BUILD_GITHUB_PLUGIN=ON
	KICAD_USE_OCE=ON
	KICAD_SPICE=ON