fixing handling of falsy valus in get_and_pass_up

lib/multi_caching.js

@@ -43,10 +43,9 @@ var multi_caching = function (caches) {
                 return cb(err);
             }
 
-            result = result || {};
             cb(err, result);
 
-            if (result && index) {
+            if (result !== undefined && index) {
                 var cachesToUpdate = caches.slice(0, index);
                 async.forEach(cachesToUpdate, function(cache, async_cb) {
                     cache.set(key, result, result.ttl, async_cb);

test/multi_caching.unit.js

@@ -202,6 +202,42 @@ describe("multi_caching", function () {
             });
         });
 
+        describe("when value is not found in any cache", function() {
+            var response;
+
+            beforeEach(function(done) {
+                key = support.random.string(10);
+                sinon.spy(memory_cache, 'set');
+                sinon.spy(memory_cache2, 'set');
+                sinon.spy(memory_cache3, 'set');
+
+                multi_cache.get_and_pass_up(key, function (err, result) {
+                    check_err(err);
+                    response = result;
+                    done();
+                });
+            });
+
+            afterEach(function() {
+                memory_cache.set.restore();
+                memory_cache2.set.restore();
+                memory_cache3.set.restore();
+            });
+
+            it("calls back with undefined", function() {
+                assert.strictEqual(response, undefined);
+            });
+
+            it("does not set anything in caches", function(done) {
+                process.nextTick(function () {
+                    assert.ok(memory_cache.set.notCalled);
+                    assert.ok(memory_cache2.set.notCalled);
+                    assert.ok(memory_cache3.set.notCalled);
+                    done();
+                });
+            });
+        });
+
         describe("using multi cache store", function () {
             beforeEach(function () {
                 multi_cache = multi_caching([memory_cache,memory_cache2,memory_cache3]);