Why does the return value of fn get dispatched?

[shaula]

I'm using redux-subscribe with plain redux (no react, no vdux or whatever).

Since I'm a redux beginner, I don't understand this line of your code:

Index: node_modules/redux-subscribe/lib/index.js
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- node_modules/redux-subscribe/lib/index.js	(revision )
+++ node_modules/redux-subscribe/lib/index.js	(revision )
@@ -85,6 +85,7 @@
 
                 if (prev !== next) {
                   (0, _foreach2.default)(function (fn) {
+                    // Why is the return value of fn dispatched again?
                     return dispatch(fn({ path: path, prev: prev, next: next }));
                   }, subscriptions[path]);
                 }

My call to subscribe looks like this:

store.dispatch(subscribe('feature', 'feature', () => {
	renderFeature();
	return {type: null};
}));

But initially I tried doing:

store.dispatch(subscribe('feature', 'feature', renderFeature));

...which failed as the dispatch function is passed a null and cannot find a property type on it. As a result I return {type: null} from my wrapped render function. Am I doing something wrong?