If a stylesheet (or a source document using the
standard tree) is built from a StreamSource with no
System ID, Saxon fails with the message "System ID
must not be null".
Circumvention is to call setSystemId("") on the
(The message is from tree.DocumentImpl line 119. The
equivalent routine in tinytree has been changed to
permit a null systemId.)
This apparently worked in 6.2.2, though I'm slightly
surprised, because null systemIds have been a
pernicious problem for a while now.