fix: fix spring gateway plugin npe (#7389)

CHANGES.md

@@ -41,6 +41,7 @@ Release Notes.
 * Remove the logic of generating instance name in `KafkaServiceManagementServiceClient` class.
 * Improve `okhttp` plugin performance by optimizing Class.getDeclaredField().
 * Fix `GRPCLogClientAppender` no context warning.
+* Fix `spring-webflux-5.x-webclient-plugin` NPE.
 
 #### OAP-Backend
 

apm-sniffer/apm-sdk-plugin/spring-plugins/spring-webflux-5.x-webclient-plugin/src/main/java/org/apache/skywalking/apm/plugin/spring/webflux/v5/webclient/WebFluxWebClientInterceptor.java

@@ -34,7 +34,6 @@ import reactor.core.publisher.Mono;
 
 import java.lang.reflect.Method;
 import java.net.URI;
-import java.util.function.BiConsumer;
 
 public class WebFluxWebClientInterceptor implements InstanceMethodsAroundInterceptorV2 {
 
@@ -79,15 +78,12 @@ public class WebFluxWebClientInterceptor implements InstanceMethodsAroundInterce
         }
         Mono<ClientResponse> ret1 = (Mono<ClientResponse>) ret;
         AbstractSpan span = (AbstractSpan) context.getContext();
-        return ret1.doAfterSuccessOrError(new BiConsumer<ClientResponse, Throwable>() {
-            @Override
-            public void accept(ClientResponse clientResponse, Throwable throwable) {
-                HttpStatus httpStatus = clientResponse.statusCode();
-                if (httpStatus != null) {
-                    Tags.STATUS_CODE.set(span, Integer.toString(httpStatus.value()));
-                    if (httpStatus.isError()) {
-                        span.errorOccurred();
-                    }
+        return ret1.doOnSuccess(clientResponse -> {
+            HttpStatus httpStatus = clientResponse.statusCode();
+            if (httpStatus != null) {
+                Tags.STATUS_CODE.set(span, Integer.toString(httpStatus.value()));
+                if (httpStatus.isError()) {
+                    span.errorOccurred();
                 }
             }
         }).doOnError(error -> {