Incorrect number of stamps by countries and categories when collection contains incomplete series

[php-coder]

Steps to reproduce:

• add a series id=2 to user's collection with only 1 stamp
• on the collection page, check statistics by categories/countries

Expected result: 1 stamp
Actual result: 2 stamps

[php-coder]

This is hard or nearly impossible to test as this statistic affects only diagrams. I'm going to write tests for DAO layer to ensure that the methods returns different numbers depending on data.

[0pdd]

@php-coder 2 puzzles #1150, #1151 are still not solved.