diff -rupN --no-dereference djvulibre-3.5.28/libdjvu/DataPool.cpp djvulibre-3.5.28-new/libdjvu/DataPool.cpp
--- djvulibre-3.5.28/libdjvu/DataPool.cpp	2020-11-20 17:57:32.000000000 +0100
+++ djvulibre-3.5.28-new/libdjvu/DataPool.cpp	2021-07-06 08:52:05.964886669 +0200
@@ -791,6 +791,8 @@ DataPool::create(const GP<DataPool> & po
   DEBUG_MSG("DataPool::DataPool: pool=" << (void *)((DataPool *)pool) << " start=" << start << " length= " << length << "\n");
   DEBUG_MAKE_INDENT(3);
 
+  if (!pool) G_THROW( ERR_MSG("DataPool.zero_DataPool") );
+
   DataPool *xpool=new DataPool();
   GP<DataPool> retval=xpool;
   xpool->init();