Event helpers add listeners directly after boot

Fixes #748

src/Silex/Application.php

@@ -267,6 +267,11 @@ class Application extends \Pimple implements HttpKernelInterface, TerminableInte
      */
     public function on($eventName, $callback, $priority = 0)
     {
+        if ($this->booted) {
+            $this['dispatcher']->addListener($eventName, $callback, $priority);
+            return;
+        }
+
         $this['dispatcher'] = $this->share($this->extend('dispatcher', function ($dispatcher, $app) use ($callback, $priority, $eventName) {
             $dispatcher->addListener($eventName, $callback, $priority);
 

tests/Silex/Tests/LazyDispatcherTest.php

@@ -38,4 +38,23 @@ class LazyDispatcherTest extends \PHPUnit_Framework_TestCase
 
         $this->assertTrue($dispatcherCreated);
     }
+
+    /** @test */
+    public function eventHelpersShouldDirectlyAddListenersAfterBoot()
+    {
+        $app = new Application();
+
+        $fired = false;
+        $app->get("/", function () use ($app, &$fired) {
+            $app->finish(function () use (&$fired) {
+                $fired = true;
+            });
+        });
+
+        $request = Request::create('/');
+        $response = $app->handle($request);
+        $app->terminate($request, $response);
+
+        $this->assertTrue($fired, 'Event was not fired');
+    }
 }