[CASSANDRA-15437] Decommission fails with "Unable to stream hints since no live endpoints seen" even if no hints need to be sent.

src/java/org/apache/cassandra/hints/HintsService.java

@@ -393,4 +393,8 @@ public boolean isShutDown()
     {
         return isShutDown;
     }
-}
+
+    public boolean hasHints()
+    {
+        return catalog.hasFiles();
+    }}

src/java/org/apache/cassandra/service/StorageService.java

@@ -4224,21 +4224,29 @@ private void unbootstrap(Runnable onFinish) throws ExecutionException, Interrupt
 
         // Start with BatchLog replay, which may create hints but no writes since this is no longer a valid endpoint.
         Future<?> batchlogReplay = BatchlogManager.instance.startBatchlogReplay();
-        Future<StreamState> streamSuccess = streamRanges(rangesToStream);
 
         // Wait for batch log to complete before streaming hints.
         logger.debug("waiting for batch log processing.");
         batchlogReplay.get();
 
         setMode(Mode.LEAVING, "streaming hints to other nodes", true);
 
-        Future hintsSuccess = streamHints();
+        if(HintsService.instance.hasHints())
+        {
+            Future<StreamState> streamSuccess = streamRanges(rangesToStream);
+            Future hintsSuccess = streamHints();
 
-        // wait for the transfer runnables to signal the latch.
-        logger.debug("waiting for stream acks.");
-        streamSuccess.get();
-        hintsSuccess.get();
-        logger.debug("stream acks all received.");
+            // wait for the transfer runnables to signal the latch.
+            logger.debug("waiting for stream acks.");
+            streamSuccess.get();
+            hintsSuccess.get();
+            logger.debug("stream acks all received.");
+        } 
+        else
+        {
+            logger.debug("no hints on the node.");
+        }
+
         leaveRing();
         onFinish.run();
     }