Sowjanya,
The reason I ask is the error is coming from this line:
var newExt = (geometryEngine.geodesicBuffer(results.extent, 10, 9002, false)).getExtent();
Which means the geometryEngine.geodesicBuffer(results.extent, 10, 9002, false) is returning null.
geodesicBuffer should only be used on WebMercator or Geographic geometry. So either the results.extent is null or is in some wkid besides WebMercator or Geographic.
Probably best to call tech support and see if this is a bug.