upgrade libs

* mongoose
* mongoose-gridfs

package.json

@@ -96,8 +96,8 @@
     "migrate-mongo": "^5.0.1",
     "mkdirp": "~0.5.1",
     "module-alias": "^2.0.6",
-    "mongoose": "^5.3.1",
-    "mongoose-gridfs": "^0.5.0",
+    "mongoose": "^5.4.4",
+    "mongoose-gridfs": "^0.6.2",
     "mongoose-paginate": "^5.0.3",
     "mongoose-unique-validator": "^2.0.2",
     "multer": "~1.4.0",

src/server/service/file-uploader/gridfs.js

@@ -97,7 +97,7 @@ module.exports = function(crowi) {
 
   lib.getFileData = async function(filePath) {
     const file = await getFile(filePath);
-    const id = file.id;
+    const id = file._id;
     const contentType = file.contentType;
     const data = await readFileData(id);
     return {