3634 fixed crash on new event
3634 fixed crash on new event

This fixes a rather subtle crash left over from the sidebar refactoring.  Creating a new event always creates an undated event, then populates the date when the photos are added in a second step. But the code to add undated events accidentally had swapped the comparator (used to sort the undated events) between the parent and child.
damianmoore/shotwell,ritchiewilson/shotwell,jof/shotwell,abrauchli/shotwell,h4ck3rm1k3/shotwell,Sanva/shotwell-gsoc,polymeris/shotwell,jimbonator/shotwell,ritchiewilson/shotwell,abrauchli/shotwell,damianmoore/shotwell,h4ck3rm1k3/shotwell,jimbonator/shotwell,ritchiewilson/shotwell,Sanva/shotwell-gsoc,jof/shotwell,h4ck3rm1k3/shotwell,Sanva/shotwell-gsoc,polymeris/shotwell,jimbonator/shotwell,polymeris/shotwell,damianmoore/shotwell,jof/shotwell,abrauchli/shotwell