cholesky: fix calc_error to prevent nan

codes/cholesky/cholesky.c

@@ -100,7 +100,7 @@ void calc_error(int n,
                 e = fabs(accurate[i][j] - test[i][j]);
             }
             /* clamp error to max 1 */
-            if(e > 1)
+            if(e > 1 || e != e)
                 e = 1;
             err += e;
             x++;