Correcting check if no path was found.
Correcting check if no path was found.

Adding comments to private method getPenaltyGraph.

edgarriba/OpenSfM,BrookRoberts/OpenSfM,oscarlorentzon/OpenSfM,mapillary/OpenSfM,BrookRoberts/OpenSfM,sunbingfengPI/OpenSFM_Test,NicWayand/OpenSfM,NicWayand/OpenSfM,oscarlorentzon/OpenSfM,edgarriba/OpenSfM,mapillary/OpenSfM,NicWayand/OpenSfM,NicWayand/OpenSfM,oscarlorentzon/OpenSfM,sunbingfengPI/OpenSFM_Test,onecue/OpenSfM,onecue/OpenSfM,edgarriba/OpenSfM,sunbingfengPI/OpenSFM_Test,mapillary/OpenSfM,BrookRoberts/OpenSfM,mapillary/OpenSfM,edgarriba/OpenSfM,sunbingfengPI/OpenSFM_Test,BrookRoberts/OpenSfM,BrookRoberts/OpenSfM,NicWayand/OpenSfM,mapillary/OpenSfM,sunbingfengPI/OpenSFM_Test,edgarriba/OpenSfM,oscarlorentzon/OpenSfM,onecue/OpenSfM,onecue/OpenSfM,onecue/OpenSfM,oscarlorentzon/OpenSfM