I can solve this problem insert tha follow instruction :
if (isNaN(g)) g = 0;
afer
if (l.prop == "height") { g = (l.now - l.start) / (l.end - l.start); }
so
...
step: function(k, l) {
if (l.prop == "height") {
g = (l.now - l.start) / (l.end - l.start);
}
if (isNaN(g)) g = 0;
j.toShow[0].style[l.prop] = (g * d
[l.prop].value) + d[l.prop].unit;
},
...

