Fix NPE in custom @InitBinder resolver initialization

Issue: SPR-14869

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/method/annotation/RequestMappingHandlerAdapter.java

@@ -273,7 +273,7 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, BeanFactory
 		resolvers.add(new ServerWebExchangeArgumentResolver());
 
 		// Custom resolvers
-		if (getCustomArgumentResolvers() != null) {
+		if (getCustomInitBinderArgumentResolvers() != null) {
 			resolvers.addAll(getCustomInitBinderArgumentResolvers());
 		}