Has Google actually indexed those pages, or just crawled them? I mean, can you search for phrases in Google and see those blank pages in the SERPs? I would be very surprised if you can. My guess is that Google has just crawled the pages but not indexed them.
In that case, I wouldn't worry too much about it. Googlebot will probably come back to visit them from time to time, but probably ignores them. It would be best to 301 redirect them to something else appropriate.
As far as pagination, I would get rid of it. Canonical every page to page 1 works fine. I'll bet your users don't use the pagination any more than Google does. Its probably best to get rid of it entirely and redirect all subsequent pages back to page 1. Here is some recent discussion about it: [webmasterworld.com...]
You are right, Google has not indexed those pages, they have just crawled.
There is another issue, we just have improved our query to increase the relevancy & quality of content in our landing pages which decreased the pages of every products but in this case plenty of indexed pages that has content earlier are now appearing empty.
I am going to 301 redirect all those empty pages to page 1 of that particular product, is that ok?