Fixed problem where, if the imported line was of zero length, OpenCascade would throw a construction error when creating a gp_Vec frmo it.  If a line is of zero length, we discard the object when reading in the line object.
Fixed problem where, if the imported line was of zero length, OpenCascade would throw a construction error when creating a gp_Vec frmo it.  If a line is of zero length, we discard the object when reading in the line object.

danheeks/heekscad,danheeks/heekscad,danheeks/heekscad,danheeks/heekscad