Merge upstream

code/datums/beam.dm

@@ -78,6 +78,7 @@
 /datum/beam/proc/Reset()
 	for(var/obj/effect/ebeam/B in elements)
 		qdel(B)
+	elements.Cut()
 
 /datum/beam/Destroy()
 	Reset()
@@ -99,7 +100,7 @@
 	for(N in 0 to length-1 step 32)//-1 as we want < not <=, but we want the speed of X in Y to Z and step X
 		var/obj/effect/ebeam/X = new beam_type(origin_oldloc)
 		X.owner = src
-		elements |= X
+		elements += X
 
 		//Assign icon, for main segments it's base_icon, for the end, it's icon+icon_state
 		//cropped by a transparent box of length-N pixel size

code/datums/diseases/advance/symptoms/fire.dm

@@ -45,7 +45,7 @@ Bonus
 	return
 
 /datum/symptom/fire/proc/Firestacks_stage_4(mob/living/M, datum/disease/advance/A)
-	var/get_stacks = (sqrt(20+A.totalStageSpeed()*2))-(sqrt(16+A.totalStealth()))
+	var/get_stacks = (sqrt(20+A.totalStageSpeed()*2))-(sqrt(max(0, 16+A.totalStealth())))
 	M.adjust_fire_stacks(get_stacks)
 	M.adjustFireLoss(get_stacks/2)
 	return 1