don't throw() during expandInstanceForEnv()

lib/app/autoload/store.client.js

@@ -141,7 +141,7 @@ YUI.add('mojito-client-store', function(Y, NAME) {
          * @param {object} ctx The runtime context.
          * @param {function} cb Callback used to return the results (or error).
          * @param {null|Error} cb.err Error encountered while attempting to service the request.
-         * @param {object} cb.instance The expanded instance.
+         * @param {object|undefined} cb.instance The expanded instance, or undefined on error.
          */
         expandInstanceForEnv: function(env, inInstance, context, callback) {
             var source = {};
@@ -155,15 +155,16 @@ YUI.add('mojito-client-store', function(Y, NAME) {
                 source.func = this._getType;
             } else {
                 // We don't have any inputs so fail
-                throw new Error('There was no "base" or "type" in the "instance" object');
+                callback(new Error('There was no "base" or "type" in the "instance" object'), undefined);
+                return;
             }
 
             // Here we get either a spec or a type.
             source.func(env, source.name, context, function(err, remoteInstance) {
                 var outInstance;
 
                 if (err) {
-                    callback(err, {});
+                    callback(err, undefined);
                     return;
                 }