Merge pull request #49 from krissss/patch-1

Fix setDescription cant be null

Author: walkor

src/Command.php

@@ -60,11 +60,14 @@ public function createCommandInstance($class_name)
             if (!$name) {
                 throw new RuntimeException("Command {$class_name} has no defaultName");
             }
-            $description = $properties['defaultDescription'] ?? '';
+            $description = $properties['defaultDescription'] ?? null;
         }
         $command = Container::get($class_name);
-        $command->setName($name)->setDescription($description);
+        $command->setName($name);
+        if ($description) {
+            $command->setDescription($description);
+        }
         $this->add($command);
         return $command;
     }
-}
+}