"This topic is empty" shown when created by an anonymous user

[johnjamesjacoby]

When anonymous posting is enabled and an anonymous user creates a new topic, the bbp_get_single_topic_description() function reports back an incorrect/unexpected string:

"This topic is empty."

[johnjamesjacoby]

Add missing condition where voice count is 0 but last-activity exists

[johnjamesjacoby]

Rev 2 - a bit cleaner, with more docs

[johnjamesjacoby]

In 7349:

Topics - Template: Add missing output condition where voice count is 0 but last-activity exists.

This change fixes a bug where topics created by anonymous users would show the "This topic is empty" fallback text in the topic description, when the topic was obviously not empty.

In trunk, for 2.7.

Fixes #3652.