Upcloud S3 does not return a Contents property if no keys are found

src/storage/s3.js

@@ -221,7 +221,7 @@ async function exists(apiConfig, backupFilePath) {
         const [error, listData] = await safe(s3.listObjectsV2(listParams));
         if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `Error listing objects ${backupFilePath}. ${formatError(error)}`);
 
-        return listData.Contents.length !== 0;
+        return listData.KeyCount !== 0 || listData.Contents.length !== 0;
     }
 }
 
@@ -334,7 +334,7 @@ async function listDir(apiConfig, dir, batchSize, marker) {
 
     const [error, listData] = await safe(s3.listObjectsV2(listParams));
     if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `Error listing objects in ${dir}. ${formatError(error)}`);
-    if (listData.Contents.length === 0) return { entries: [], marker: null }; // no more
+    if (listData.KeyCount === 0 || listData.Contents.length === 0) return { entries: [], marker: null }; // no more
     const entries = listData.Contents.map(function (c) { return { fullPath: c.Key, size: c.Size }; });
     return { entries, marker: !listData.IsTruncated ? null : listData.NextContinuationToken };
 }