Handle getting out-of-bounds bits in get_bit (#574)

The binary state is not padded with zeroes, so they must be inferred.

mesecons/util.lua

@@ -164,7 +164,9 @@ end
 
 function mesecon.get_bit(binary,bit)
 	bit = bit or 1
-	local c = binary:len()-(bit-1)
+	local len = binary:len()
+	if bit > len then return false end
+	local c = len-(bit-1)
 	return binary:sub(c,c) == "1"
 end