Conversion from type DBNull to type String was not valid

This article describes a product issue when creating a new catalog entry content with a content selector metadata. The complete error would look like the sample below.

Timestamp: 1/18/2016 8:36:23 PM
Message: Exception thrown from: /WorkArea/medialist.aspx?action=ViewLibraryByCategory&actionType=library&autonavfolder=-1&scope=&autonav=%5c&dentrylink=0&EditorName=&enhancedmetaselect=1&selectids=&selecttitles=&separator=&metadataformtagid=4True
Conversion from type 'DBNull' to type 'String' is not valid. at Microsoft.VisualBasic.CompilerServices.Conversions.ToString(Object Value)
at Ektron.Cms.DataIO.EkContentRW.GetFolderParentFolderIdRecursive(Int64 folderid) at Microsoft.VisualBasic.CompilerServices.Conversions.ToString(Object Value)
at Ektron.Cms.DataIO.EkContentRW.GetFolderParentFolderIdRecursive(Int64 folderid)

This issue was resolved in a cumulative update.

9.10 SP2 Site Update
Update 15 (January 29, 2016)

23632 - Conversion from type DBNull to type String was not valid when you added a catalog entry with a content selector.

It can be downloaded here. For more instruction please see here.