Fix for missing transactions in getWalletTransactions() response

The previous criteria was to stop searching for more leaf keys as soon as we found a batch of keys with no transactions, but it seems that there are occasions when subsequent batches do actually contain transactions. The solution/workaround is to require 5 consecutive empty batches before giving up. There may be ways to improve this further by copying approaches from other BIP32 implementations, but this is a quick fix that should solve the problem for now.

src/main/java/org/qortal/crosschain/Bitcoiny.java

@@ -351,6 +351,10 @@ public List<SimpleTransaction> getWalletTransactions(String key58) throws Foreig
 		Set<BitcoinyTransaction> walletTransactions = new HashSet<>();
 		Set<String> keySet = new HashSet<>();
 
+		// Set the number of consecutive empty batches required before giving up
+		final int numberOfAdditionalBatchesToSearch = 5;
+
+		int unusedCounter = 0;
 		int ki = 0;
 		do {
 			boolean areAllKeysUnused = true;
@@ -374,9 +378,19 @@ public List<SimpleTransaction> getWalletTransactions(String key58) throws Foreig
 				}
 			}
 
-			if (areAllKeysUnused)
-				// No transactions for this batch of keys so assume we're done searching.
-				break;
+			if (areAllKeysUnused) {
+				// No transactions
+				if (unusedCounter >= numberOfAdditionalBatchesToSearch) {
+					// ... and we've hit our search limit
+					break;
+				}
+				// We haven't hit our search limit yet so increment the counter and keep looking
+				unusedCounter++;
+			}
+			else {
+				// Some keys in this batch were used, so reset the counter
+				unusedCounter = 0;
+			}
 
 			// Generate some more keys
 			keys.addAll(generateMoreKeys(keyChain));