[Patch] Small grammatical fix in the ticket_email_mimic.html email

[Jae Chang]

I have a picky user that complained about this line in the html email:

• Resolution changed from [shouldn't something be here?] to Fixed.

The old resolution was simply a <blank> value. Thus the patch simply checks for a value before printing the preceding "from".

Now, if the old resolution has no value, it becomes:

• Resolution changed to Fixed.

[Steffen Hoffmann]

(In [12345]) TracAnnouncer: Improve ticket change notification template, refs #8620.

Feels like there must be more corner-cases, that are not handled optimal now, but this is an easy win, so won't miss it for older announcer versions as well.

Thanks to jc2trachacks for taking care to report as well as for providing a good starting point towards the actual fix (omit the empty old value too).

[Steffen Hoffmann]

Couldn't resist to do that change, especially for such a remarkable change number.

[Ryan J Ollos]

Please upgrade to Trac 1.2, which has integrated the core of AnnouncerPlugin. Please raise the issue on the ​trac:MailingList if you encounter the issue with Trac 1.2.