fix: work correctly on pre-parsed AsyncAPI docs when given as Input

lib/utils.js

@@ -6,9 +6,10 @@ const parser = require('@asyncapi/parser');
  * @param {Array} asyncApiDocs unparsed AsyncAPI documents
  * @returns {Promise<Array>} parsed AsyncAPI documents
  */
+
 function validate(asyncApiDocs) {
   return Promise.all(asyncApiDocs.map(async doc => {
-    if (doc && doc['x-parser-spec-parsed'] === true) {
+    if (typeof doc === 'object' && doc.ext && doc.ext('x-parser-spec-parsed')) {
       return doc;
     }
     return parser.parse(doc);