Crash when editing an application whose icon was deleted

[DavidBriscoe]

Setting and externally deleting an icon causes alacarte to crash when editing that application.

Edit Applications > Gvim
Set /mnt/shared/icon-gvim.png as the icon
In Terminal, mv /mnt/shared/icon-gvim.png /mnt/shared/icons/icon-gvim.png
Accessories > Gvim > Properties

Actual:
Crash. Alacarte doesn't close, but the preferences window never opens and I get a "alacarte has crashed" popup window. Subsequent attempts to edit Properties of Gvim do nothing. Clicking Properties for other applications still works.

Expected:
Icon is automatically set to empty, loaded with a ? placeholder, or I get an error message with an option to clear the set icon.

Thanks for making a great gui for editing applications! It's nice to have a simple streamlined editor for customization.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: alacarte 3.44.1-1ubuntu0.1
ProcVersionSignature: Ubuntu 6.5.0-26.26~22.04.1-generic 6.5.13
Uname: Linux 6.5.0-26-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.5
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Sat Mar 23 11:16:48 2024
InstallationDate: Installed on 2024-03-23 (0 days ago)
InstallationMedia: Ubuntu 22.04.4 LTS "Jammy Jellyfish" - Release amd64 (20240220)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_CA:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: alacarte
UpgradeStatus: No upgrade log present (probably fresh install)