Added test to confirm merging an Object and null behaves as expected.

test/fixtures/merge/file1.json

@@ -12,5 +12,8 @@
       "first": 1,
       "second": 2
     }
+  },
+  "unicorn": {
+    "exists": true
   }
 }

test/fixtures/merge/file2.json

@@ -5,5 +5,6 @@
     "something4": true
   },
   "dates": true,
-  "elderberries": true
+  "elderberries": true,
+  "unicorn": null
 }

test/provider-test.js

@@ -84,6 +84,11 @@ vows.describe('nconf/provider').addBatch({
           provider.merge(override);
           helpers.assertMerged(null, provider.stores.file.store);
           assert.equal(provider.stores.file.store.candy.something, 'file1');
+        },
+        "should merge Objects over null": function (provider) {
+          provider.load();
+          provider.merge(override);
+          assert.equal(provider.stores.file.store.unicorn.exists, true);
         }
       }
     }