check that waiting queue exists before calling forEach on it (jaredwray#69)

Author: BryanDonovan

Diff for: lib/callback_filler.js

@@ -6,9 +6,11 @@ CallbackFiller.prototype.fill = function(key, err, data) {
     var waiting = this.queues[key];
     delete this.queues[key];
 
-    waiting.forEach(function(task) {
-        (task.cb)(err, data);
-    });
+    if (waiting && waiting.length) {
+        waiting.forEach(function(task) {
+            (task.cb)(err, data);
+        });
+    }
 };
 
 CallbackFiller.prototype.has = function(key) {

Diff for: test/caching.unit.js

@@ -515,6 +515,19 @@ describe("caching", function() {
                 });
             });
 
+            context("when callback called twice by client", function() {
+                it("it does not throw an error", function(done) {
+                    cache.wrap(key, function(cb) {
+                        methods.getWidget(name, cb);
+                        methods.getWidget(name, cb);
+                    }, opts, function(err, widget) {
+                        checkErr(err);
+                        assert.deepEqual(widget, {name: name});
+                        setTimeout(done, 10);
+                    });
+                });
+            });
+
             it("lets us make nested calls", function(done) {
                 function getCachedWidget(name, cb) {
                     cache.wrap(key, function(cacheCb) {