0027063: BRepGProps raises exception on edge with no curves

0027063: BRepGProps raises exception on edge with no curves

Method BRepGProp::LinearProperties() is corrected to treat not geometric edges (their length is zero). To avoid wrong working of command nexplode global properties are calculated as point properties of vertexes. Small value Epsilon(1.) is used as density of points. This prevents exception on shapes that contain such edges, e.g. copy of a wire containing degenerated edge.

Method BRep_Tool::IsGeometric() is optimized to avoid nested iteration for check of 3D curve for Null.
Small bug is fixed in GProp_PGProps.cxx