Invalid task with a non-existing image [likely the containing folder in Azure] is created when syncing azure cloud storage

**Describe the bug**
When I do a cloud-sync with an azure blob storage there is always an empty task created even if there is no image in the cloud storage available.

It is not created if I set a File Filter Regex.

**To Reproduce**
Steps to reproduce the behavior:
1. Setup a project with a Microsoft Azure Source storage using a prefix (e.g. labelstudio/input) and Treat every bucket object as a source file enabled.
2. Upload one image to the blob
3. Press sync in labelstudio
4. Open the tasks of the project
5. There are two tasks

**Expected behavior**
Only one task should show up

**Screenshots**
Blob Storage:

Tasks:

**Environment (please complete the following information):**
- Linux (hosted on Azure as webapp)
- Label Studio Version 1.13.1