Fix offering Sandstorm grains without a title

packages/rocketchat-oembed/client/oembedSandstormGrain.coffee

@@ -7,8 +7,11 @@ Template.oembedSandstormGrain.helpers
 		return @meta.sandstorm.grain.grainTitle
 	appIconUrl: ->
 		return @meta.sandstorm.grain.appIconUrl
+	descriptor: ->
+		return @meta.sandstorm.grain.descriptor
 window.sandstormOembed = (e) ->
 	e = e or window.event
 	src = e.target or e.srcElement
 	token = src.getAttribute "data-token"
-	Meteor.call "sandstormOffer", token
+	descriptor = src.getAttribute "data-descriptor"
+	Meteor.call "sandstormOffer", token, descriptor

packages/rocketchat-oembed/client/oembedSandstormGrain.html

@@ -3,7 +3,8 @@
 		<label>
 			<h3>{{grainTitle}}</h3>
 			<img src="{{appIconUrl}}" />
-			<button onclick="sandstormOembed(event)" data-token="{{token}}">
+			<button onclick="sandstormOembed(event)" data-token="{{token}}"
+							data-descriptor="{{descriptor}}">
 				Click to open the grain
 			</button>
 		</label>

packages/rocketchat-sandstorm/server/powerbox.js

@@ -7,12 +7,15 @@ if (process.env.SANDSTORM === '1') {
 	var Powerbox = Npm.require('sandstorm/powerbox.capnp');
 	var Grain = Npm.require('sandstorm/grain.capnp');
 
-	RocketChat.Sandstorm.offerUiView = function(token, sessionId) {
+	RocketChat.Sandstorm.offerUiView = function(token, seriliazedDescriptor, sessionId) {
 		var httpBridge = getHttpBridge();
 		var session = httpBridge.getSessionContext(sessionId).context;
 		var api = httpBridge.getSandstormApi(sessionId).api;
 		var cap = waitPromise(api.restore(new Buffer(token, 'base64'))).cap;
-		return waitPromise(session.offer(cap, undefined, {tags: [{id: '15831515641881813735'}]}));
+		return waitPromise(session.offer(cap, undefined, {tags: [{
+			id: '15831515641881813735',
+			value: new Buffer(seriliazedDescriptor, 'base64'),
+		}]}));
 	};
 
 	Meteor.methods({
@@ -33,11 +36,13 @@ if (process.env.SANDSTORM === '1') {
 				token: newToken,
 				appTitle: appTitle,
 				appIconUrl: appIconUrl,
-				grainTitle: grainTitle
+				grainTitle: grainTitle,
+				descriptor: descriptor.tags[0].value.toString('base64'),
 			};
 		},
-		sandstormOffer: function(token) {
-			RocketChat.Sandstorm.offerUiView(token, this.connection.sandstormSessionId());
+		sandstormOffer: function(token, seriliazedDescriptor) {
+			RocketChat.Sandstorm.offerUiView(token, seriliazedDescriptor,
+				this.connection.sandstormSessionId());
 		}
 	});
 }