Thanks again! It worked! But I put the catch line just before the delete line, I suppose the catch line was set to "start up" the data source so that it won't be null?
Regarding the re-query, I used by original buttons. Just that the rules went: 1) Query Data connection 2) Insert search query 3) Query Data connection. Previously, I only had 2) and 3) but now I've added 1) to re-initialize the data connection. An extra rule but a required one if I deleted the data connection on reset.