Sorry to retrieve this thread,It very clearly says "HAD a valid study permit", meaning that your study permit had to be valid when you applied for the PGWP.
Seriously, it is very clearly written that you can continue working. I don't know why you are trying to cause yourself problems.
I applied for my PGWP on Sept 8th and my study permit will expire on Nov 1st. I understand that by right I am on implied status now, however I read from this link http://www.cic.gc.ca/english/helpcentre/questions-answers-by-topic.asp?st=15.5 that:
If the new application was submitted for a different type of temporary resident status (e.g., work permit):
- On the expiry of your study permit you must stop any of the activities stated in the original study permit once the permit expires. For example, you may have come to Canada as a student and then applied for a work permit. If so, you must stop studying once your study permit expires. After that, you cannot work or study until you get a new permit.