From c7dfe5931704d351dcfe736ca46c79a414b4b857 Mon Sep 17 00:00:00 2001
From: Andreas Schildbach <andreas.schildbach@bloq.com>
Date: Tue, 19 Mar 2019 18:01:18 +0100
Subject: [PATCH] KeyChainGroup: Fix NullPointerException in
 findRedeemDataFromScriptHash() if no deterministic keychain is in the group.

---
 .../java/org/bitcoinj/wallet/KeyChainGroup.java    | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/core/src/main/java/org/bitcoinj/wallet/KeyChainGroup.java b/core/src/main/java/org/bitcoinj/wallet/KeyChainGroup.java
index 18be8580..586b88be 100644
--- a/core/src/main/java/org/bitcoinj/wallet/KeyChainGroup.java
+++ b/core/src/main/java/org/bitcoinj/wallet/KeyChainGroup.java
@@ -502,12 +502,14 @@ public class KeyChainGroup implements KeyBag {
     @Override
     @Nullable
     public RedeemData findRedeemDataFromScriptHash(byte[] scriptHash) {
-        // Iterate in reverse order, since the active keychain is the one most likely to have the hit
-        for (Iterator<DeterministicKeyChain> iter = chains.descendingIterator() ; iter.hasNext() ; ) {
-            DeterministicKeyChain chain = iter.next();
-            RedeemData redeemData = chain.findRedeemDataByScriptHash(ByteString.copyFrom(scriptHash));
-            if (redeemData != null)
-                return redeemData;
+        if (chains != null) {
+            // Iterate in reverse order, since the active keychain is the one most likely to have the hit
+            for (Iterator<DeterministicKeyChain> iter = chains.descendingIterator(); iter.hasNext();) {
+                DeterministicKeyChain chain = iter.next();
+                RedeemData redeemData = chain.findRedeemDataByScriptHash(ByteString.copyFrom(scriptHash));
+                if (redeemData != null)
+                    return redeemData;
+            }
         }
         return null;
     }