GH-1234 Add delegation to existing shouldFailIfCantConvert(..)

This ensures that if Throwable is not provided it can fal back to already implemented method

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/config/MessageConverterHelper.java

@@ -44,6 +44,9 @@ public interface MessageConverterHelper {
 	 * @return true if conversion failure must be considered fatal.
 	 */
 	default boolean shouldFailIfCantConvert(Message<?> message, Throwable t) {
+		if (t == null) {
+			return this.shouldFailIfCantConvert(message);
+		}
 		return false;
 	}