Comment # 4 on bug 955146 from Mark Fairbairn

I'm still on plasma 5.4.2
changing the line

switch (currentIndex) {
to
switch (index) {

completely broke system tray show/hide function for me. Making changes to show
/ hide had no effect - e.g. setting dropbox icon to always hide made no
difference and it remained showing in the tray. Reverting the change I could
then set to hide - but the behaviour of reappearing on reboot persists.
I'll try changing the suggested line again in 5.4.3 when that is pushed out to
leap.