Schematic editor: assertion in debug build

Description

Attempt to edit symbol from schematics rises assertion

Steps to reproduce

1. open schematic editor, load schematics
2. select any symbol, open properties dialog
3. press "Edit symbol"

KiCad Version

Application: KiCad Schematic Editor

Version: (6.99.0-5009-g321de57d7c), debug build

Libraries:
	wxWidgets 3.0.5
	FreeType 2.11.1
	HarfBuzz 2.7.4
	FontConfig 2.13.1

Platform: Linux 5.15.0-53-generic x86_64, 64 bit, Little endian, wxGTK, cinnamon, x11

	wxWidgets: 3.0.5 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.74.0
	OCC: 7.5.1
	Curl: 7.81.0
	ngspice: 37+
	Compiler: GCC 11.3.0 with C++ ABI 1016

Build settings:
	KICAD_SPICE=ON
	KICAD_STDLIB_DEBUG=OFF
	KICAD_STDLIB_LIGHT_DEBUG=OFF
	KICAD_SANITIZE_ADDRESS=OFF
	KICAD_SANITIZE_THREADS=OFF