Update dependencies, fixing flow error

Author: leebyron

package.json

@@ -42,14 +42,14 @@
     "babel": "5.8.21",
     "babel-runtime": "^5.8.x",
     "babel-core": "5.8.22",
-    "babel-eslint": "4.0.10",
-    "chai": "3.2.0",
-    "coveralls": "2.11.3",
-    "eslint": "1.1.0",
-    "eslint-plugin-babel": "^2.1.1",
-    "flow-bin": "0.14.0",
+    "babel-eslint": "4.1.6",
+    "chai": "3.4.1",
+    "coveralls": "2.11.6",
+    "eslint": "1.10.3",
+    "eslint-plugin-babel": "2.2.0",
+    "flow-bin": "0.20.1",
     "isparta": "3.0.3",
-    "mocha": "2.2.5",
-    "sane": "1.1.3"
+    "mocha": "2.3.4",
+    "sane": "1.3.0"
   }
 }

src/index.js

@@ -65,8 +65,11 @@ export default class DataLoader<K, V> {
     var shouldCache = !options || options.cache !== false;
 
     // If caching and there is a cache-hit, return cached Promise.
-    if (shouldCache && this._promiseCache.has(key)) {
-      return this._promiseCache.get(key);
+    if (shouldCache) {
+      var cachedPromise = this._promiseCache.get(key);
+      if (cachedPromise) {
+        return cachedPromise;
+      }
     }
 
     // Otherwise, produce a new Promise for this value.