Refactor some importprunedfunds checks with guard clause

Credit to jkczyz

Author: Antoine Riard

src/wallet/rpcdump.cpp

@@ -363,31 +363,26 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
     //Search partial merkle tree in proof for our transaction and index in valid block
     std::vector<uint256> vMatch;
     std::vector<unsigned int> vIndex;
-    unsigned int txnIndex = 0;
-    Optional<int> height;
-    if (merkleBlock.txn.ExtractMatches(vMatch, vIndex) == merkleBlock.header.hashMerkleRoot) {
-
-        auto locked_chain = pwallet->chain().lock();
-        height = locked_chain->getBlockHeight(merkleBlock.header.GetHash());
-        if (height == nullopt) {
-            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found in chain");
-        }
-
-        std::vector<uint256>::const_iterator it;
-        if ((it = std::find(vMatch.begin(), vMatch.end(), hashTx))==vMatch.end()) {
-            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Transaction given doesn't exist in proof");
-        }
+    if (merkleBlock.txn.ExtractMatches(vMatch, vIndex) != merkleBlock.header.hashMerkleRoot) {
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Something wrong with merkleblock");
+    }
 
-        txnIndex = vIndex[it - vMatch.begin()];
+    auto locked_chain = pwallet->chain().lock();
+    Optional<int> height = locked_chain->getBlockHeight(merkleBlock.header.GetHash());
+    if (height == nullopt) {
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found in chain");
     }
-    else {
-        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Something wrong with merkleblock");
+
+    std::vector<uint256>::const_iterator it;
+    if ((it = std::find(vMatch.begin(), vMatch.end(), hashTx)) == vMatch.end()) {
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Transaction given doesn't exist in proof");
     }
 
+    unsigned int txnIndex = vIndex[it - vMatch.begin()];
+
     CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, *height, merkleBlock.header.GetHash(), txnIndex);
     wtx.m_confirm = confirm;
 
-    auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     if (pwallet->IsMine(*wtx.tx)) {