adds null-value definition in VOTable for Long and Integer columns

data-discovery/src/main/java/webapi/formatfilter/ObscoreExt.java

@@ -43,7 +43,7 @@ class ObscoreExt
 
       new ColumnInfo( "access_url",     String.class, "Access URL" ),
       new ColumnInfo( "access_format",  String.class, "Format (MIME type)" ),
-      new ColumnInfo( "access_estsize", Long.class,   "Extimated size (KB)" ),
+      genLongWithNullColInfo("access_estsize", "Extimated size (KB)" ),
 
       new ColumnInfo( "target_name", String.class,  "Target" ),