Do not allow to close eeschema when local symbol editor is opened

Description

4556D

Steps to reproduce

1. In eeschema: CTRL + E on symbol, local symbol editor is opened;
2. Click on Exit "X" button in eeschema (while symbol editor still running);
3. Eeschema (asks if schematics changes needs to be saved) closes, but child window, "Local symbol editor" is left opened.

It is not clear what will be done when pressing save in symbol editor in this situation..

Eeschema window should not be available to be closed when it has CTRL+E'd symbol editor opened.

• But please, do not make symbol editor modal, it is useful to navigate through schematics with local symbol edito opened.

KiCad Version

Application: KiCad Schematic Editor (64-bit)

Version: (6.0.0-rc2-1-g6f711f8ce3), release build

Libraries:
	wxWidgets 3.1.5
	libcurl/7.78.0-DEV Schannel zlib/1.2.11

Platform: Windows 10 (build 19042), 64-bit edition, 64 bit, Little endian, wxMSW

Build Info:
	Date: Dec 17 2021 05:59:32
	wxWidgets: 3.1.5 (wchar_t,wx containers)
	Boost: 1.76.0
	OCC: 7.5.0
	Curl: 7.78.0-DEV
	ngspice: 35
	Compiler: Visual C++ 1929 without C++ ABI

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON