Calling duplicate operation without selecting anything registers an undo step. If nothing is selected (keyframe, curve, object, etc.), cancel the operator execution to prevent undo push. Patch improves following operators: - ACTION_OT_duplicate - GPENCIL_OT_duplicate - GRAPH_OT_duplicate - MESH_OT_duplicate - NODE_OT_duplicate - OBJECT_OT_duplicate Reviewed By: campbellbarton Ref D14511