Set corpus as null attribute

foo.sh

@@ -7,7 +7,8 @@ cwb-encode \
   -f /root/files/corpus.vrt \
   -R /usr/local/share/cwb/registry/corpus \
   -P lemma -P simple_pos -P pos -P ner \
-  -S corpus -S text:0+author+id+publishing_year+title -S s \
+  -S text:0+author+id+publishing_year+title -S s \
+  -0 corpus \
   -xsB
 cwb-make \
   -V CORPUS