boostorg/geometry — pull request #184 by mkaravel (2014-12-05 15:24:50+00:00)
Title: Fix/validity of empty multigeometries

This PR changes the validity check for multi-geometries: multi-geometries with no elements are now considered as valid.
The unit test for `bg::is_valid` is also updated, as well as the document, which now reflects this change.