Makes medibeams more resilient to lag (#69919)

code/datums/beam.dm

@@ -118,8 +118,7 @@
 	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
 		if(QDELETED(src))
 			break
-		var/obj/effect/ebeam/segment = new beam_type(origin_turf)
-		segment.owner = src
+		var/obj/effect/ebeam/segment = new beam_type(origin_turf, src)
 		elements += segment
 
 		//Assign our single visual ebeam to each ebeam's vis_contents
@@ -165,6 +164,10 @@
 	anchored = TRUE
 	var/datum/beam/owner
 
+/obj/effect/ebeam/Initialize(mapload, beam_owner)
+	owner = beam_owner
+	return ..()
+
 /obj/effect/ebeam/update_overlays()
 	. = ..()
 	var/mutable_appearance/emmisive = emissive_appearance(icon, icon_state)

code/modules/projectiles/guns/special/medbeam.dm

@@ -123,6 +123,13 @@
 				qdel(dummy)
 				return FALSE
 		for(var/obj/effect/ebeam/medical/B in next_step)// Don't cross the str-beams!
+			if(QDELETED(current_beam))
+				break //We shouldn't be processing anymore.
+			if(QDELETED(B))
+				continue
+			if(!B.owner)
+				stack_trace("beam without an owner! [B]")
+				continue
 			if(B.owner.origin != current_beam.origin)
 				explosion(B.loc, heavy_impact_range = 3, light_impact_range = 5, flash_range = 8, explosion_cause = src)
 				qdel(dummy)