I've found a bug in master and after bisecting it looks like you've
introduced it.

> 39d37fafcce29160c4dfe6ef7696de19bebb1d18 is the first bad commit

To reproduce:

* Enable configuration storage
* Activate tracking on any table with default options
* Go back to the database in which the table in question is
* Select the tracking tab
* Click "Drop" near the tracking entry you created
* You will get an internal server error

From my error.log:

roccivic@gentile-desktop:~/www/pma$ tail -n 1 /var/log/apache2/error.log
[Wed Aug 01 19:10:31 2012] [error] [client 127.0.0.1] PHP Fatal error:
Call to undefined function PMA_query_as_controluser() in
/home/roccivic/www/pma/libraries/Tracker.class.php on line 374, referer:
http://localhost/pma/db_tracking.php?db=test3&token=f01096a0fa6885a13fcc19946b6359f8

Thanks for pointing that.
Seems I have missed one place while renaming a function.
I just correct this in my repository and now bug should be fixed. (I couldn't reproduce the error)

Regards !

Chanaka