Update user-defined error handling for async and default response res…

…olution

index.js

@@ -434,7 +434,15 @@ alexa.app = function(name) {
     })
     .catch(function(e) {
       if (typeof self.error == "function") {
-        return self.error(e, request, response);
+        // Default behavior of any error handler is to send a response
+        return Promise.resolve(self.error(e, request, response)).then(function() {
+            if (!response.resolved) {
+                response.resolved = true;
+                return response.send();
+            }
+            // propagate successful response if it's already been resolved
+            return response.response;
+        });
       } else if (typeof e == "string" && self.messages[e]) {
         if (!request.isAudioPlayer()) {
           response.say(self.messages[e]);

test/test_alexa_app_unknown_type_request.js

@@ -63,7 +63,7 @@ describe("Alexa", function() {
         it("responds with a spoken message for uncaught errors in the globally defined error function and resolves", function() {
           testApp.error = function(e, request, response) {
             response.say("Sorry, something bad happened");
-            response.send();
+            return response.send();
           };
 
           var subject = testApp.request(mockRequest).then(function(response) {
@@ -78,7 +78,7 @@ describe("Alexa", function() {
         it("responds with a spoken message for uncaught errors in the globally defined error function and fails", function() {
           testApp.error = function(e, request, response) {
             response.say("Sorry, something bad happened");
-            response.fail(e);
+            return response.fail(e);
           };
 
           var subject = testApp.request(mockRequest).then(function(response) {