Use module.require to avoid webpack complaints about unmet dependencies.

apollographql/apollo-client#3589 (comment)

lib/local.js

@@ -1,24 +1,21 @@
 "use strict";
 
-var fakeNullFiber = function Fiber(){};
+var fakeNullFiber = new (function Fiber(){});
 var localKey = "_optimism_local";
 
 function getCurrentFiber() {
   return fakeNullFiber;
 }
 
-try {
-  var fiberPath = require.resolve("fibers");
-} catch (e) {}
-
-if (fiberPath) {
-  var Fiber = require(fiberPath);
-
-  // If we were able to require("fibers"), redefine the getCurrentFiber
-  // function so that it has a chance to return Fiber.current.
-  getCurrentFiber = function () {
-    return Fiber.current || fakeNullFiber;
-  };
+if (typeof module === "object") {
+  try {
+    var Fiber = module.require("fibers");
+    // If we were able to require fibers, redefine the getCurrentFiber
+    // function so that it has a chance to return Fiber.current.
+    getCurrentFiber = function () {
+      return Fiber.current || fakeNullFiber;
+    };
+  } catch (e) {}
 }
 
 // Returns an object unique to Fiber.current, if fibers are enabled.