I can confirm the error on Ubuntu 10.04, Trac 0.11.7, TracTicketStatsPlugin 2.1, and Firefox 3.6.8.
The error I see in the Firefox Error Console is:
Error: YAHOO.widget.LogReader is not a constructor
Source File: http://localhost:8000/tracdev/ticketstats
I patched as you suggested:
However, now there is an error console at the bottom of the page:
The logger code is form lines 145:149,
var myLogReader = new YAHOO.widget.LogReader("myLogger");
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