message: Set viewFrustum member even if not valid - it is necessary to access
  viewState from viewport (sheets did not work etc.)
diff: @@ -653,8 +653,7 @@ export class ViewFrustum {
  }
  public static createFromViewport(vp: Viewport, view?: ViewState): ViewFrustum | undefined {
  - const vf = new ViewFrustum(view !== undefined ? view : vp.view, vp.canvas.clientWidth, vp.canvas.clientHeight);
  - return vf.invalidFrustum ? undefined : vf;
  + return new ViewFrustum(view !== undefined ? view : vp.view, vp.canvas.clientWidth, vp.canvas.clientHeight);
  }
  public static createFromViewportAndPlane(vp: Viewport, plane: Plane3dByOriginAndUnitNormal): ViewFrustum | undefined {
  