Fix automatic embedding of asynchronous plugins (jsonp)

Closes #540

js/plugin-directive.js

@@ -47,8 +47,12 @@ weechat.directive('plugin', ['$rootScope', 'settings', function($rootScope, sett
                 // TODO store the result between channel switches
                 if ($scope.plugin.content instanceof Function){
                     // Don't rerun if the result is already there
-                    if (embed.innerHTML === "") {
-                        $scope.plugin.content();
+                    if (!embed || embed.innerHTML === "") {
+                        // if we're autoshowing, the element doesn't exist yet, and we need
+                        // to do this async (wrapped in a setTimeout)
+                        setTimeout(function() {
+                            $scope.plugin.content();
+                        });
                     }
                 } else {
                     $scope.displayedContent = $scope.plugin.content;