Various Null Access Fixes (#22730)

<img width="1420" height="776" alt="image"
src="https://github.com/user-attachments/assets/d33c4ce2-9c5b-48c3-ac8b-5edfee51c7e0"
/>

Just a few fixes for some various runtime errors and two hard del
triggers on the Sentry logs.

code/game/objects/effects/chem/chemsmoke.dm

@@ -153,13 +153,11 @@
 		var/mobnames = ""
 		if (touched_mobs.len > 1)
 			mobnames += "Affected players: "
-			var/i = 1
-			do
+			var/num_players = length(touched_mobs)
+			for (var/i = 1, i <= num_players, i++)
 				mobnames += "<A href='byond://?_src_=holder;adminmoreinfo=[REF(touched_mobs[i])]'>?</a>"
-				if (touched_mobs[i+1])
+				if (i < num_players)
 					mobnames += ", "
-				i++
-			while (touched_mobs[i])
 			mobnames += "."
 		else mobnames += "Affected player: [touched_mobs[1]]."
 		var/containing = ""