Incorrect query generated when filter is passed to activity_get_activity

An incorrect query is genrated when filters are passed to the activity_get_activity. This is not evident all the times. The problem lies with the loop that traverses through the filter (around line 290):

foreach ($filter as $criteria => $values) {

The values are assigned to the strings array and the array persists through the loop.
The fix is to reinitialize the strings array at the start of every loop iteration.

$strings=array()