Several little fixes

- Fix custom missiles causing a crash if graphic not found
- Fix display in transcript of damage taken by monsters
- Fix missile start items not having their missile graphic set
- Fix immunity fields being signed (which would've prevented immunities from working properly)
- Don't bother generating a random number if min and max are the same
- Fix monster attack types not showing right
- Fix checking for item abilities returning 0 instead of 24 when not found
- Fix not updating screen when switching active PC

src/boe.items.cpp

@@ -238,7 +238,7 @@ short pc_has_abil_equip(short pc_num,eItemAbil abil,short dat) {
 		if(dat >= 0 && dat != univ.party[pc_num].items[i].abil_data[1]) continue;
 		return i;
 	}
-	return 0;
+	return 24;
 }
 
 short pc_has_abil(short pc_num,eItemAbil abil,short dat) {
@@ -248,7 +248,7 @@ short pc_has_abil(short pc_num,eItemAbil abil,short dat) {
 		if(dat >= 0 && dat != univ.party[pc_num].items[i].abil_data[1]) continue;
 		return i;
 	}
-	return 0;
+	return 24;
 }
 
 bool party_has_abil(eItemAbil abil,short dat) {