return NullCounter when read via Cascading, but not within a cluster side job

While implementing a parquet provider for Cascading lingual (http://docs.cascading.org/lingual/1.1/#provider) I ran into the case, where the counters would be null and I got a NPE. 

The problem is triggered by an optimization in lingual, where it would not create a hadoop job to read the file, but directly stream the data over (no where clause). It will not happen in a Cascading app, that is submitted to the cluster. 

The patch handles this case.