#5291 package sources with platform options are ignored

[Logmod]

Webmin cannot read/interpret platform options in the package repository menu.
Example: "deb [arch=amd64] https://download.docker.com/linux/debian buster stable" to sources.list is not shown in the web GUI.

Also adding a platform option to the URL in the Webmin GUI is not supported and results in an error "Missing or invalid-looking base URL".