If I use "Join attributes by location" from the menu it works fine but if I'm using it within the Processing modeler it's not working.
I want to sum up previously selected records having a field area (calculated by "Export/add geometry columns").
Surprisingly, the sum fields are created but all records contain NULL.
Did I miss something? Any well known bug which I haven't found with Google? Do these two algorithm works differently?
BTW: If I run "Join attributes by location" from the processing toolbox, the algorithm works fine too.
(I'm using QGIS 2.8.1-Wien.)