[FIX] calendar: Don't halt on non existant constraint
[FIX] calendar: Don't halt on non existant constraint

OpenUpgrade/OpenUpgrade,OpenUpgrade/OpenUpgrade,Endika/OpenUpgrade,grap/OpenUpgrade,Endika/OpenUpgrade,grap/OpenUpgrade,OpenUpgrade/OpenUpgrade,OpenUpgrade/OpenUpgrade,OpenUpgrade/OpenUpgrade,grap/OpenUpgrade,grap/OpenUpgrade,grap/OpenUpgrade,Endika/OpenUpgrade,grap/OpenUpgrade,Endika/OpenUpgrade,Endika/OpenUpgrade,grap/OpenUpgrade,Endika/OpenUpgrade,Endika/OpenUpgrade,OpenUpgrade/OpenUpgrade,OpenUpgrade/OpenUpgrade