Added safegaurd against invalid project id in the method getFileContent

Author: thegitone23

server/controllers/file.controller.js

@@ -110,7 +110,7 @@ export function deleteFile(req, res) {
 
 export function getFileContent(req, res) {
   Project.findById(req.params.project_id, (err, project) => {
-    if (err) {
+    if (err || project == null) {
       res.status(404).send({ success: false, message: 'Project with that id does not exist.' });
       return;
     }