I upgraded a site from 5.6.2 to version 6. All seems ok, but during the upgrade an error in the sql provider highlighted in red. I checked the log and copied the following info. Please tell me if I should do something and what should I do?

System.Data.SqlClient.SqlException: Cannot insert the value NULL into column 'Folder', table 'tenniscoachl_yfvf.dbo.Files'; column does not allow nulls. UPDATE fails. The statement has been terminated. at System.Data.SqlClient.SqlConnection. (SqlException exception, Boolean breakConnection) at System.Data.SqlClient.SqlInternalConnection. (SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async) at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) at System.Data.SqlClient.SqlCommand.ExecuteNonQuery() at DotNetNuke.Data.SqlDataProvider.ExecuteADOScript(String SQL) at DotNetNuke.Data.SqlDataProvider.ExecuteScript(String Script, Boolean UseTransactions) ALTER TABLE dbo.[Files] ALTER COLUMN [Folder] NVARCHAR(246) NOT NULL

Thanks Sebastian. Prior to reading your suggestion I looked at the table via ssms and the column "folders" was already there but set at nvarchar200 I believe. I changed it to 246. I believe that is what the script wants to do?