Keep in mind NULL in the database is not the same as an empty string '', reporting tools will show NULL as a blank space because they don't really know what else to show them as.

If you want yes you can set that column to not allow nulls at the database level but that will first require you cleaning up all the existing nulls in your database and then presumably working with whoever is populating that column so they know what they have to set that column to, if you just add that constraint without telling anyone people will start getting hard errors from the database whenever they try to write a null value.

What problems exactly is this causing?