Error on download notification after module upgrade

[stetard]

Describe the bug

After upgrade the module from 3.5.6 to 4.1.1, the file download doesn't work anymore.

Software Versions

• DNN: 09.13.00
• Module: 04.01.01

To Reproduce

Steps to reproduce the behavior:

1. Upgrade an old website using the 3.5.6 version to the 4.1.1
2. Click on the download link for a file listed by an existing module (created with the old version)
3. The error message is:
   [NullReferenceException: Object reference not set to an instance of an object.]
   DotNetNuke.Modules.Repository.Repository.SendDownloadNotification(RepositoryInfo objRepository)

Expected behavior

User should obtain the selected file when clicking on the download link.

[stetard]

I think this issue is caused by the feature #42 which can send notifications when a user downloads a file.
In my case, the module settings haven't been updated manualy nor programaticaly.
I will provide a fix which will consist to test if the corresponding setting exists in the database before using its value.