Properly handle non-finite position

If either position is NaN, the `makeSkyWcs` call further down will fail
because `skyCenter` is also NaN.

src/table/wcsUtils.cc

@@ -93,6 +93,9 @@ void updateRefCentroids(geom::SkyWcs const &wcs, ReferenceCollection &refList) {
 
 Eigen::Matrix2f calculateCoordCovariance(geom::SkyWcs const &wcs, lsst::geom::Point2D center,
                                          Eigen::Matrix2f err) {
+    if (!isfinite(center.getX()) || !isfinite(center.getY())) {
+        return Eigen::Matrix2f::Constant(NAN);
+    }
     // Get the derivative of the pixel-to-sky transformation, then use it to
     // propagate the centroid uncertainty to coordinate uncertainty. Note that
     // the calculation is done in arcseconds, then converted to radians in