Consistently check DispatcherType to avoid NPE in tests

Closes gh-26602

spring-web/src/main/java/org/springframework/web/filter/OncePerRequestFilter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -145,7 +145,7 @@ public abstract class OncePerRequestFilter extends GenericFilterBean {
 	 * @see WebAsyncManager#hasConcurrentResult()
 	 */
 	protected boolean isAsyncDispatch(HttpServletRequest request) {
-		return request.getDispatcherType().equals(DispatcherType.ASYNC);
+		return DispatcherType.ASYNC.equals(request.getDispatcherType());
 	}
 
 	/**