Runtime fixes:

runtime error: list index out of bounds
proc name: attack (/obj/item/weapon/gun/projectile/russian/attack)

runtime error: Cannot read null.loc
proc name: Topic (/mob/living/silicon/pai/Topic)

I've also added Pewter to the list of spriters.

git-svn-id: http://tgstation13.googlecode.com/svn/trunk@4553 316c924e-a436-60f5-8080-3fe189b3f50e

code/modules/mob/living/silicon/pai/software.dm

@@ -198,6 +198,7 @@
 				var/mob/living/M = src.loc
 				var/count = 0
 				while(!istype(M, /mob/living))
+					if(!M || !M.loc) return 0 //For a runtime where M ends up in nullspace (similar to bluespace but less colourful)
 					M = M.loc
 					count++
 					if(count >= 6)