In Controller.processIncomingTransactionsQueue(), don't bother with 2nd-phase of locking blockchain and importing if there are no valid signature transactions to actually import

src/main/java/org/qortal/controller/Controller.java

@@ -847,7 +847,7 @@ public class Controller extends Thread {
 
 	private void processIncomingTransactionsQueue() {
 		if (this.incomingTransactions.isEmpty()) {
-			// Don't bother locking if there are no new transactions to process
+			// Nothing to do?
 			return;
 		}
 
@@ -912,6 +912,11 @@ public class Controller extends Thread {
 				sigValidTransactions.add(transaction);
 			}
 
+			if (sigValidTransactions.isEmpty()) {
+				// Don't bother locking if there are no new transactions to process
+				return;
+			}
+
 			try {
 				ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
 				if (!blockchainLock.tryLock(2, TimeUnit.SECONDS)) {