Optimize events using nullsafe operator (#5473)

Author: huangdijia

src/Command.php

@@ -419,9 +419,9 @@ protected function execute(InputInterface $input, OutputInterface $output)
 
         $callback = function () {
             try {
-                $this->eventDispatcher && $this->eventDispatcher->dispatch(new Event\BeforeHandle($this));
+                $this->eventDispatcher?->dispatch(new Event\BeforeHandle($this));
                 $this->handle();
-                $this->eventDispatcher && $this->eventDispatcher->dispatch(new Event\AfterHandle($this));
+                $this->eventDispatcher?->dispatch(new Event\AfterHandle($this));
             } catch (Throwable $exception) {
                 if (class_exists(ExitException::class) && $exception instanceof ExitException) {
                     return $this->exitCode = (int) $exception->getStatus();
@@ -436,7 +436,7 @@ protected function execute(InputInterface $input, OutputInterface $output)
                 $this->eventDispatcher->dispatch(new Event\FailToHandle($this, $exception));
                 return $this->exitCode = (int) $exception->getCode();
             } finally {
-                $this->eventDispatcher && $this->eventDispatcher->dispatch(new Event\AfterExecute($this));
+                $this->eventDispatcher?->dispatch(new Event\AfterExecute($this));
             }
 
             return 0;