wxSFLineShape::SetStartingConnectionPoint does not update the source shape ID

[iwbnwif]

When setting a line's starting point to a connection point, it is also necessary to separately update the source shape's ID.

There does not appear to be a good reason for this, so I propose to add:

SetSrcShapeId(cp->GetParentShape()->GetId()); to the wxSFLineShape::SetStartingConnectionPoint method and similarly SetTrgShapeId(cp->GetParentShape()->GetId()); to the wxSFLineShape::SetEndingConnectionPoint method.

Both additions should be made within the guarding 'if' statement.