[Backport #2008 to 5.x] Make AbstractAnnotation::$_context non-nullable (#2009)

---------

Co-authored-by: kriss <462679766@qq.com>
Co-authored-by: DerManoMann <mano@radebatz.net>

Author: 3 people

src/Annotations/AbstractAnnotation.php

@@ -36,7 +36,7 @@ abstract class AbstractAnnotation implements \JsonSerializable
     public $attachables = Generator::UNDEFINED;
 
     /**
-     * @var Context|null
+     * @var Context
      */
     public $_context;
 

src/Processors/Concerns/DocblockTrait.php

@@ -17,10 +17,6 @@ trait DocblockTrait
      */
     public function isDocblockRoot(OA\AbstractAnnotation $annotation): bool
     {
-        if (!$annotation->_context) {
-            return true;
-        }
-
         if (1 == count($annotation->_context->annotations)) {
             return true;
         }