Daily e-mail notifications in 4.1 doesn't show umlauts correctly

Summary of Bug

When receiving daily notification e-mails from Confluence 4.1, if the subject of the e-mail contains umlauts, it will not be rendered correctly

Steps to reproduce

1. Enable 'Subscribe to daily updates'
2. Ensure that there have been changes in the instance, and then either wait for the daily e-mail to be sent, or force it to run (scheduled jobs)
3. Check the subject of the e-mail to see if it is rendered correctly

Findings

• This is a screenshot of how the e-mail looks like :
  
• I have tested receiving this mail using both gmail and ymail, and both of them are affected