cvpcb text filter box loses focus when search results change

Description

The cvpcb footprint text filter textbox loses focus whenever the filtered footprint list changes, which is after almost every character entered. This makes it frustrating to use because you have to click into it after entering nearly every letter.

I vaguely recall a similar issue with the add symbol filter?

Steps to reproduce

1. Open cvpcb
2. Disable all footprint filters
3. type "battery" into the filter textbox - you'll have to refocus the text box after most letters, unless adding an additional letter doesn't change the filtered results (like "ry" in "battery")

KiCad Version

Application: KiCad Schematic Editor

Version: (6.0.7-rc1-155-g9b15717349), release build

Libraries:
	wxWidgets 3.2.1
	libcurl/7.85.0 OpenSSL/1.1.1q zlib/1.2.12 brotli/1.0.9 zstd/1.5.2 libidn2/2.3.3 libpsl/0.21.1 (+libidn2/2.3.0) libssh2/1.10.0 nghttp2/1.49.0

Platform: Linux 5.15.68-1-lts x86_64, 64 bit, Little endian, wxGTK, KDE, x11

Build Info:
	Date: Sep  7 2022 23:32:54
	wxWidgets: 3.2.0 (wchar_t,wx containers) GTK+ 3.24
	Boost: 1.79.0
	OCC: 7.5.3
	Curl: 7.85.0
	ngspice: 37
	Compiler: GCC 12.2.0 with C++ ABI 1017

Build settings:
	KICAD_USE_OCC=ON
	KICAD_USE_EGL=ON
	KICAD_SPICE=ON