Don't broadcast any arbitrary signatures if the list is empty (i.e. the node isn't yet hosting anything)

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataManager.java

@@ -369,12 +369,12 @@ public class ArbitraryDataManager extends Thread {
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			List<ArbitraryTransactionData> hostedTransactions = ArbitraryDataStorageManager.getInstance().listAllHostedTransactions(repository);
 			List<byte[]> hostedSignatures = hostedTransactions.stream().map(ArbitraryTransactionData::getSignature).collect(Collectors.toList());
-
+			if (!hostedSignatures.isEmpty()) {
 				// Broadcast the list, using null to represent our peer address
 				LOGGER.info("Broadcasting list of hosted signatures...");
 				Message arbitrarySignatureMessage = new ArbitrarySignaturesMessage(null, 0, hostedSignatures);
 				Network.getInstance().broadcast(broadcastPeer -> arbitrarySignatureMessage);
-
+			}
 		} catch (DataException e) {
 			LOGGER.error("Repository issue when fetching arbitrary transaction data for broadcast", e);
 		}