Fix crash on MissingToken (phpactor#2049)

Co-authored-by: Vladimír Dudr <vladimir@tango-dj.cz>

Author: vlada-dudr

lib/Indexer/Adapter/Tolerant/Indexer/ClassDeclarationIndexer.php

@@ -2,6 +2,7 @@
 
 namespace Phpactor\Indexer\Adapter\Tolerant\Indexer;
 
+use Microsoft\PhpParser\MissingToken;
 use Microsoft\PhpParser\Node;
 use Phpactor\Indexer\Model\Name\FullyQualifiedName;
 use Phpactor\Indexer\Model\Record\ClassRecord;
@@ -56,6 +57,11 @@ private function indexBaseClass(Index $index, ClassRecord $record, ClassDeclarat
             return;
         }
 
+        /** @phpstan-ignore-next-line */
+        if ($baseClass instanceof MissingToken) {
+            return;
+        }
+
         $name = $baseClass->getResolvedName();
         $record->addImplements(FullyQualifiedName::fromString((string)$name));
         $baseClassRecord = $index->get(ClassRecord::fromName($name));