[5.x] Replaced a too strict assertion in DatabaseSessionHandler.php that prevented to use the sessions at all with a more simple sanity check. Test already failed on that, now they pass.

Author: Toni Vega

src/Session/MongoDbSessionHandler.php

@@ -56,9 +56,9 @@ public function read($sessionId): string|false
                 'typeMap' => ['root' => 'bson'],
             ],
         );
-        assert($result instanceof Document);
 
-        return $result ? (string) $result->payload : false;
+
+        return $result?->payload ? (string) $result->payload : false;
     }
 
     public function write($sessionId, $data): bool