[SOLVED]assertion for null node

Hi,

I use getDomNodes to get multiple nodes.
before extracting values i want to make sure the node is not null.
def videodescr = holder.getDomNodes( " //aetgt:GetVideoMetaDataResponse/aetgt:GetVideoMetaDataResult/aetgt:VideoMetadata/aetgt:Video/@Title" )
assert videodescr != null.

The above assertion doesnt work.

What is the step or function i can use to check that nodes are not null.