[sfm/pipelines] Fix return value for the regions_provider.
[sfm/pipelines] Fix return value for the regions_provider.

openMVG/openMVG,openMVG/openMVG,openMVG/openMVG,poparteu/openMVG,poparteu/openMVG,openMVG/openMVG,poparteu/openMVG,openMVG/openMVG,poparteu/openMVG