Return early from composed Converter if initial conversion step returned null

See gh-23379

Author: jhoeller

spring-core/src/main/java/org/springframework/core/convert/converter/Converter.java

@@ -57,8 +57,11 @@ public interface Converter<S, T> {
 	 * @since 5.3
 	 */
 	default <U> Converter<S, U> andThen(Converter<? super T, ? extends U> after) {
-		Assert.notNull(after, "after must not be null");
-		return (S s) -> after.convert(convert(s));
+		Assert.notNull(after, "After Converter must not be null");
+		return (S s) -> {
+			T initialResult = convert(s);
+			return (initialResult != null ? after.convert(initialResult) : null);
+		};
 	}
 
 }