Fix null relation problem (#2319)

* Add null check for relation type map.

For relations that are not explicitly defined in the schema, we need a null check here.

* Making change to force rebuild.

* Reverting change.

* Adds test

src/Controllers/DatabaseController.js

@@ -1,4 +1,4 @@
-// A database adapter that works with data exported from the hosted
+// A database adapter that works with data exported from the hosted
 // Parse database.
 
 import intersect from 'intersect';
@@ -121,7 +121,7 @@ DatabaseController.prototype.loadSchema = function() {
 DatabaseController.prototype.redirectClassNameForKey = function(className, key) {
   return this.loadSchema().then((schema) => {
     var t = schema.getExpectedType(className, key);
-    if (t.type == 'Relation') {
+    if (t && t.type == 'Relation') {
       return t.targetClass;
     } else {
       return className;