Enable conversation open when app started offline (#2064)

Turns out textsecure.messaging is only set up on first connection to the
server. When we start up offline, we never do that. And it prevents the
user from opening every conversation.

There's a whole lot more to do to bulletproof ourselves against a
missing textsecure.messaging (and then beyond that, queuing outgoing
messages so they don't get dropped completely when offline).

Hence, it's a band-aid.

js/models/conversations.js

@@ -911,6 +911,11 @@
     },
 
     getProfile: function(id) {
+        if (!textsecure.messaging) {
+            var message = 'Conversation.getProfile: textsecure.messaging not available';
+            return Promise.reject(new Error(message));
+        }
+
         return textsecure.messaging.getProfile(id).then(function(profile) {
             var identityKey = dcodeIO.ByteBuffer.wrap(profile.identityKey, 'base64').toArrayBuffer();