Writing of SentEmail returns an error when using attachments

[kneibdev]

When attaching files from assets/* the SentEmail object couldn't be written.

Message:

`ERROR [User Error]: Uncaught SS_DatabaseException: Couldn't run query:

UPDATE "SentEmail" SET "To" = ?, "From" = ?, "Subject" = ?, "Body" = ?, "SerializedEmail" = ?, "LastEdited" = ?, "Created" = ?, "ClassName" = ?

WHERE ("ID" = ?)

Lost connection to MySQL server during query`