Nullchecks. And one zero division.

code/game/objects/items/devices/taperecorder.dm

@@ -124,8 +124,8 @@
 		usr << "<span class='notice'>You can't clear the memory while playing or recording!</span>"
 		return
 	else
-		storedinfo -= storedinfo
-		timestamp -= timestamp
+		if(storedinfo)	storedinfo.Cut()
+		if(timestamp)	timestamp.Cut()
 		timerecorded = 0
 		usr << "<span class='notice'>Memory cleared.</span>"
 		return

code/modules/admin/verbs/adminsay.dm

@@ -25,7 +25,7 @@
 	for (var/client/C in admin_list)
 		if (src.holder.rank == "Admin Observer")
 			C << "<span class='adminobserver'><span class='prefix'>ADMIN:</span> <EM>[key_name(usr, C)]:</EM> <span class='message'>[msg]</span></span>"
-		else if(C.holder.level != 0)
+		else if(C.holder && C.holder.level != 0)
 			C << "<span class='admin'><span class='prefix'>ADMIN:</span> <EM>[key_name(usr, C)]</EM> (<A HREF='?src=\ref[C.holder];adminplayerobservejump=\ref[mob]'>JMP</A>): <span class='message'>[msg]</span></span>"
 
 /client/proc/cmd_mod_say(msg as text)

code/modules/paperwork/paper.dm

@@ -226,7 +226,7 @@
 
 /obj/item/weapon/paper/Topic(href, href_list)
 	..()
-	if((usr.stat || usr.restrained()))
+	if(!usr || (usr.stat || usr.restrained()))
 		return
 
 	if(href_list["write"])

code/modules/power/smes.dm

@@ -61,7 +61,7 @@
 
 
 /obj/machinery/power/smes/proc/chargedisplay()
-	return round(5.5*charge/capacity)
+	return round(5.5*charge/(capacity ? capacity : 5e6))
 
 #define SMESRATE 0.05			// rate of internal charge to external power
 

code/modules/research/xenoarchaeology/artifact_analysis.dm

@@ -221,7 +221,7 @@
 				findarti++
 				cur_artifact = A
 			if (findarti == 1)
-				if(cur_artifact.being_used)
+				if(cur_artifact && cur_artifact.being_used)
 					var/message = "<b>[src]</b> states, \"Cannot analyse. Excess energy drain is disrupting signal.\""
 					src.visible_message(message, message)
 				else