Remove unnecessary function call

index.js

@@ -18,12 +18,10 @@ module.exports = function simpleSinkStream(_options) {
 		required,
 		wrapValueAsOption("onResult"), {
 			onResult: [ required, isFunction ],
+			onAbort: [ isFunction ],
 			onEnd: [ isFunction, defaultTo.literal(function defaultOnEnd() {
 				// We return whatever value we got last from the specified onResult callback.
 				return lastResult;
-			})],
-			onAbort: [ isFunction, defaultTo.literal(function defaultOnAbort() {
-				// no-op
 			})]
 		}
 	]);
@@ -88,7 +86,9 @@ module.exports = function simpleSinkStream(_options) {
 					abortHandled = true;
 
 					return Promise.try(() => {
-						return onAbort();
+						if (onAbort != null) {
+							return onAbort();
+						}
 					}).then(() => {
 						if (marker.reason instanceof Error) {
 							// NOTE: This ensures that the original error causing the abort is thrown exactly once