Most likely com_zimbra_email didn't get re-added properly.
First try clearing the browser cache & running zmprov flushCache zimlet.
If that doesnt work test by disabling the zimlet on cos/domain/user, and if you don't get that error anymore:
Un-deploy your current com_zimbra_email zimlet, make sure all it's files are gone from /opt/zimbra/zimlets-deployed etc, grab the new one from the patch and install it.
Bug 45852 – Unable to open some attached messages