From db735a598ffd5ddb3faccf0412e5069cecefe8ad Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Mon, 22 Oct 2018 05:24:13 +1100
Subject: [PATCH] Fix underflow in shuffle with empty list

---
 beacon_chain/utils/shuffling/src/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/beacon_chain/utils/shuffling/src/lib.rs b/beacon_chain/utils/shuffling/src/lib.rs
index 91a3a73e2..9691240f8 100644
--- a/beacon_chain/utils/shuffling/src/lib.rs
+++ b/beacon_chain/utils/shuffling/src/lib.rs
@@ -34,7 +34,7 @@ pub fn shuffle<T>(
         return Ok(list);
     }
 
-    for i in 0..(list.len() - 1) {
+    for i in 0..(list.len().saturating_sub(1)) {
         let n = list.len() - i;
         let j = rng.rand_range(n as u32) as usize + i;
         list.swap(i, j);