Merge pull request #1243 from violetagg/write-issue

* SPR-14941:
  Fix NPE in ServletServerHttpResponse.ResponseBodyProcessor.write

spring-web/src/main/java/org/springframework/http/server/reactive/AbstractResponseBodyProcessor.java

@@ -221,11 +221,13 @@ abstract class AbstractResponseBodyProcessor implements Processor<DataBuffer, Vo
 				if (dataBuffer.readableByteCount() == 0) {
 					processor.subscription.request(1);
 				}
-				else if (processor.changeState(this, RECEIVED)) {
+				else {
 					processor.receiveBuffer(dataBuffer);
+					if (processor.changeState(this, RECEIVED)) {
 						processor.writeIfPossible();
 					}
 				}
+			}
 
 			@Override
 			public void onComplete(AbstractResponseBodyProcessor processor) {