Footprint editor crashes editing pad shape if save is attempted before finishing edit

Description

When editing a pad shape in the footprint editor, if an attempt is made to save the footprint before finishing the pad edit, the footprint editor will crash.

Steps to reproduce

1. In the footprint editor, load the footprint "crash_demo", attached.
2. Select pad 1
3. From the right-click menus, select "Edit pad as graphic shapes"
4. select the polygon around pad 1
5. Try to save the footprint (File->save, or ctrl-s or cmd-s)
6. This should produce a crash.
7. Pad 2 shows that the pad can be creaed properly if the edit is finished before saving.

1.Crash_demo.kicad_mod 2.

KiCad Version

Version: (6.0.5-0), release build

Libraries:
	wxWidgets 3.1.5
	libcurl/7.79.1 SecureTransport (LibreSSL/3.3.5) zlib/1.2.11 nghttp2/1.45.1

Platform: macOS Version 12.3.1 (Build 21E258), 64 bit, Little endian, wxMac

Build Info:
	Date: May  3 2022 12:26:25
	wxWidgets: 3.1.5 (wchar_t,wx containers)
	Boost: 1.78.0
	OCC: 7.6.2
	Curl: 7.64.1
	ngspice: 35
	Compiler: Clang 12.0.0 with C++ ABI 1002

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON