diff --git a/code/game/objects/devices/PDA/cart.dm b/code/game/objects/devices/PDA/cart.dm
index ef012e92fdd..2461604742a 100644
--- a/code/game/objects/devices/PDA/cart.dm
+++ b/code/game/objects/devices/PDA/cart.dm
@@ -515,8 +515,9 @@ Code:
 					for (var/obj/item/weapon/mop/M in world)
 						var/turf/ml = get_turf(M)
 
-						if (ml.z != cl.z)
-							continue
+						if(ml)
+							if (ml.z != cl.z)
+								continue
 
 						ldat += "Mop - <b>\[[ml.x],[ml.y]\]</b> - [M.reagents.total_volume ? "Wet" : "Dry"]<br>"
 
diff --git a/code/game/objects/structures.dm b/code/game/objects/structures.dm
index a7fc4875349..8f19124f02f 100644
--- a/code/game/objects/structures.dm
+++ b/code/game/objects/structures.dm
@@ -84,7 +84,9 @@ obj/structure
 				Tsrc.ReplaceWithWall()
 				for(var/obj/machinery/atmospherics/pipe/P in Tsrc)
 					P.layer = 1
-				W:use(2)
+				for(var/turf/simulated/wall/X in Tsrc.loc)
+					if(X)	X.add_hiddenprint(usr)
+				if (W)	W:use(2)
 				del(src)
 			return
 
@@ -99,6 +101,8 @@ obj/structure
 					Tsrc.ReplaceWithRWall()
 					for(var/obj/machinery/atmospherics/pipe/P in Tsrc)
 						P.layer = 1
+					for(var/turf/simulated/wall/r_wall/X in Tsrc.loc)
+						if(X)	X.add_hiddenprint(usr)
 					if (W)
 						W:use(1)
 					del(src)
diff --git a/code/modules/mob/living/carbon/metroid/life.dm b/code/modules/mob/living/carbon/metroid/life.dm
index 13ec9d07430..737872121ca 100644
--- a/code/modules/mob/living/carbon/metroid/life.dm
+++ b/code/modules/mob/living/carbon/metroid/life.dm
@@ -359,7 +359,10 @@
 					Tempstun = 1
 
 				if(bodytemperature <= (T0C - 50)) // hurt temperature
-					adjustFireLoss(round(sqrt(bodytemperature)) * 2)
+					if(bodytemperature <= 50) // sqrting negative numbers is bad
+						adjustFireLoss(200)
+					else
+						adjustFireLoss(round(sqrt(bodytemperature)) * 2)
 
 			else
 				Tempstun = 0
diff --git a/code/modules/mob/mob_movement.dm b/code/modules/mob/mob_movement.dm
index b1888dadd89..aebdcb2a1d0 100644
--- a/code/modules/mob/mob_movement.dm
+++ b/code/modules/mob/mob_movement.dm
@@ -215,16 +215,17 @@
 				if(L.len == 2)
 					L -= mob
 					var/mob/M = L[1]
-					if ((get_dist(mob, M) <= 1 || M.loc == mob.loc))
-						var/turf/T = mob.loc
-						. = ..()
-						if (isturf(M.loc))
-							var/diag = get_dir(mob, M)
-							if ((diag - 1) & diag)
-							else
-								diag = null
-							if ((get_dist(mob, M) > 1 || diag))
-								step(M, get_dir(M.loc, T))
+					if(M)
+						if ((get_dist(mob, M) <= 1 || M.loc == mob.loc))
+							var/turf/T = mob.loc
+							. = ..()
+							if (isturf(M.loc))
+								var/diag = get_dir(mob, M)
+								if ((diag - 1) & diag)
+								else
+									diag = null
+								if ((get_dist(mob, M) > 1 || diag))
+									step(M, get_dir(M.loc, T))
 				else
 					for(var/mob/M in L)
 						M.other_mobs = 1