Single LED broken on 12V LED bar?
It is best to feed the string which in your case has normaly 3 leds in series with a current source  this stops led current rising steeply with increasing supply volts and stops current falling significantly unless supply volts go below about 10 which is unlikely   NOW you can safely place a zener across each LED which is just above the max LED forward volts   Example  3V9 for white led  This is all cheap because the current source could be a two terminal IC or discrete transistor circuit and the zener doesn't have to be high power  In fact all parts can be SMD so parts count isn't a penalty