InternalParquetRecordReader.close() should not throw an exception if initialization has failed

InternalParquetRecordReader.close() currently throws a NullPointerException if initialize() didn't succeed and hence the "reader" remains null.

This NPE happens with client usage idioms like this:

AvroParquetReader reader = ...
try {
       // read some parquet data
} finally {
  if (reader != null) { reader.close(); }
}

I believe close() should read as follows:

public void close() throws IOException {
    if (reader != null) {
      reader.close();
    }
  }

Thoughts?