Bug 511710

STEPS TO REPRODUCE:
1. Place a .desktop file with a valid URL on the KDE desktop
2. Click the .desktop file to open URL in Firefox (in different Activity)
3. Plasma panels and desktop controls disappear

OBSERVED RESULT:
- All panels and screen-edge/corner controls stop responding
- journalctl shows:
  file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:81: 
  TypeError: Cannot read property 'endsWith' of undefined

EXPECTED RESULT:
- Controls should remain functional
- Function should handle undefined iconName gracefully

SOFTWARE VERSIONS:
Arch Linux
KDE Plasma 6.x
Wayland session

ADDITIONAL INFORMATION:
The symbolicizeIconName() function in main.qml (line 81) doesn't check if iconName 
is defined before calling .endsWith(). Suggested fix: add null/undefined check at 
function start.

$ plasmashell --version
>>>>>
plasmashell 6.5.1
QThreadStorage: entry 8 destroyed before end of thread 0x558f9e6c4010
QThreadStorage: entry 2 destroyed before end of thread 0x558f9e6c4010
QThreadStorage: entry 1 destroyed before end of thread 0x558f9e6c4010
<<<<<

$uname -a
>>>>>
Linux hog5 6.17.6-arch1-1 #1 SMP PREEMPT_DYNAMIC Wed, 29 Oct 2025 22:23:47 +0000 x86_64 GNU/Linux
<<<<<

$ inxi -S
>>>>>
System:
  Host: mememe Kernel: 6.17.6-arch1-1 arch: x86_64 bits: 64
  Desktop: KDE Plasma v: 6.5.1 Distro: Arch Linux
<<<<<

$ journalctl /usr/bin/plasmashell
>>>>>
[..]
Nov 06 13:24:24 mememe plasmashell[1673]: file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:81: TypeError: Cannot read property 'endsWith' of undefined
<<<<<