Diagnosis
You want to delete the last packaging assignment of the only article
version. The article can only be stored with at least one valid
packaging. Otherwise it must be selected for deletion entirely.

Procedure
If you want to delete all of the packagings for the article, execute
the "Select for deletion" function in the initial screen of the
"Change article" transaction. The article is then preselected for
deletion in the specified company code and country for the selected
sales unit. If you only want to replace the selected packaging with
another packaging, assign the new packaging first and then delete the
packaging assignment you have selected.