Long sync time related to archives lacking 'date_added' tag

[aoyin1106]

In the past few weeks, I suffered from slow sync time taking more than 5 minutes once I fully reopened the app.

Today I found that some of my archives do not have a metadata tag called "date_added", making them inproperly shown at the top of stack when sorted by date (I also sort archives by date in Ichaival). After manually adding the date tag, the long sync time problem magically disappears. I can stably reproduce the long sync problem by removing "date_added" tag from an archive.

Just to share my experience in case someone else meets a similar problem. Further, maybe some robustness improvements could be made.