Also returning in the warnings

Author: joshuakgoldberg

packages/react/src/ReactHooks.js

@@ -99,6 +99,7 @@ export function useEffect(
       create != null,
       'useEffect must be called with a create function, but null or undefined was passed.',
     );
+    return;
   }
 
   return dispatcher.useEffect(create, inputs);
@@ -115,6 +116,7 @@ export function useLayoutEffect(
       create != null,
       'useLayoutEffect must be called with a create function, but null or undefined was passed.',
     );
+    return;
   }
 
   return dispatcher.useLayoutEffect(create, inputs);