Yes, it will happen if you disable tags after setting a non-zero minimum. You should be able to fix it by modifying qa-page-ask.php as follows:
$in['tags']=qa_get_tags_field_value('tags');
... to ...
if (qa_using_tags()) $in['tags']=qa_get_tags_field_value('tags');
The fix will be rolled into Q2A 1.6.2.