Delete multiple symbol properties problem

Description

When trying to delete multiple properties of a symbol in the "Symbol Properties" dialog.

1. Pressing the "Delete" key in the keyboard - values in the "Name" columns are deleted but there are still entries
2. Pressing "Delete field" button - deletes the first selected item and not all of the selected. Moreover, pressing again the "Delete field" button will try to delete to (FirstSelectedIndex-1) and not the second one.

Steps to reproduce

1. Select symbol in schematics and press "e" to open the "Symbol Properties" dialog
2. Select the 1st property to remove, hold the Control key and select the last property to be removed
3. Press the "Delete" key (in keyboard)
4. Repeat steps 1-2
5. Press the "Delete field" button
6. Press the "Delete field" button again

KiCad Version

Application: KiCad (64-bit)

Version: (6.0.0-rc1-400-gd1e6c216e1), release build

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

Platform: Windows 10 (build 19044), 64-bit edition, 64 bit, Little endian, wxMSW

Build Info:
	Date: Dec 11 2021 09:00:14
	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