Added curly braces for if refract in ch10 of _InOneWeekend_

Author: Trevor Black

books/RayTracingInOneWeekend.html

@@ -1284,8 +1284,9 @@
                      outward_normal = rec.normal;
                      ni_over_nt = 1.0 / ref_idx;
                 }
-                if (refract(r_in.direction(), outward_normal, ni_over_nt, refracted))
+                if (refract(r_in.direction(), outward_normal, ni_over_nt, refracted)) {
                    scattered = ray(rec.p, refracted);
+                }
                 else {
                    scattered = ray(rec.p, reflected);
                    return false;