Make sure data is migrated before leaving registration page

www/user/main.js

@@ -227,13 +227,26 @@ define([
                             proxy[k] = map[k];
                         });
 
+                        var whenSynced = function () {
                             delete localStorage.FS_hash;
 
                             if (!proxy[USERNAME_KEY]) {
                                 proxy[USERNAME_KEY] = opt.name;
                             }
-
                             next();
+                        };
+
+                        // Make sure the migration is synced in chainpad before continuing otherwise
+                        // we may leave that page too early or trigger a reload in another tab before
+                        // the migration is complete
+                        var check = function () {
+                            if (APP.realtime.getUserDoc() === APP.realtime.getAuthDoc()) {
+                                whenSynced();
+                                return;
+                            }
+                            window.setTimeout(check, 300);
+                        };
+                        check();
                     });
                 });
             });