set preImgObject = {'image': {}} for initializing preImgObject

backstage/static/js/parsers.js

@@ -61,6 +61,7 @@ function parseMd(content) {
       if (line.includes('</amp-img>')) {
         blockArray = addDataToBlockArray(preImgObject, blockArray, preBlockindex, imgDataIndex);
         isAmpImgRange = false;
+        preImgObject = {'image': {}}
         continue;
       }
       imgDataIndex = preDataIndex;