When attempting to unparse an infoset via the CLI, a NullPointer exception occurs.

Note from Steve: "This is caused when we read an infoset from a tree rather than XML (I believe the TDML tests use XML, CLI uses a tree). When we use a tree, there's a bug in the code where the XML stream isn't properly initialized. We just need to fix that bug."

To reproduce:
To save the parser/unparser:
daffodil-cli/target/universal/stage/bin/daffodil save-parser -s daffodil-test/src/test/resources/edu/illinois/ncsa/daffodil/section00/general/generalSchema.dfdl.xsd --root e1 > e1.parser.bin
To test out unparser using file input:
echo '<tns:e1 xmlns:tns="http://www.example.org/example1/">Hello</tns:e1>' > input
daffodil-cli/target/universal/stage/bin/daffodil unparse --parser e1.parser.bin input