Error in DTBook conversion, "A sequence of more than one item is not allowed as the second argument of concat()"

What steps will reproduce the problem?
1. Run the script dtbook-to-epub3 with the sample DAISY input.
- The sample that demonstrates this is a copyrighted work, so I have shared it 
privately with Romain in Dropbox: 
https://www.dropbox.com/s/hz8rz3nh0v839ln/Delight_in_the_Details_DAISY_Clean.zip
2. Sample script:
cli/dp2 dtbook-to-epub3 --i-source ./Delight_in_the_Details.xml \
   --data /Users/john/testing/epub3/Delight_in_the_Details_DAISY_Clean.zip \
   --file /Users/john/testing/epub3/Delight_in_the_Details_DAISY_Clean-output.zip \
   --x-assert-valid false \
   > /Users/john/testing/epub3/Delight_in_the_Details_DAISY_Clean-client.log

What is the expected output? What do you see instead?
The conversion fails during the dtbook-to-zedai step. I've attached the full 
job log, but here is the relevant error section:
2013-10-04 14:06:50,299 [INFO ] o.d.c.xproc.calabash.steps.Message - 
bundle://29.0:1/xml/dtbook-to-zedai.convert.xpl:563:33:Message:file:/opt/pipelin
e2/current/data/data/b5e57076-9c24-4d80-88b1-bdc3d30f28a0/context/images/9781599
630854_0130_001.jpg --> 
file:/opt/pipeline2/current/data/data/b5e57076-9c24-4d80-88b1-bdc3d30f28a0/outpu
t/output-dir/zedai/images/9781599630854_0130_001.jpg
2013-10-04 14:06:50,305 [DEBUG] o.d.c.xproc.calabash.steps.Message - 
bundle://29.0:1/xml/dtbook-to-zedai.convert.xpl:563:33:Message step 
!1.72.6.1.3.7 read 
file:/opt/pipeline2/current/data/data/b5e57076-9c24-4d80-88b1-bdc3d30f28a0/conte
xt/Delight_in_the_Details.xml
2013-10-04 14:06:52,948 [DEBUG] o.d.c.xproc.calabash.steps.Message - Running 
{http://xmlcalabash.com/ns/extensions}message !1.70
2013-10-04 14:06:52,948 [INFO ] o.d.c.xproc.calabash.steps.Message - 
bundle://29.0:1/xml/dtbook-to-zedai.convert.xpl:521:49:Message:Conversion 
complete.
2013-10-04 14:06:52,955 [DEBUG] o.d.c.xproc.calabash.steps.Message - 
bundle://29.0:1/xml/dtbook-to-zedai.convert.xpl:521:49:Message step !1.70 read 
file:/opt/pipeline2/current/data/data/b5e57076-9c24-4d80-88b1-bdc3d30f28a0/conte
xt/Delight_in_the_Details.xml
2013-10-04 14:06:53,832 [ERROR] com.xmlcalabash.library.XSLT - 
bundle://18.0:1/xml/xslt/html-chunker.xsl:22:err:XPTY0004:A sequence of more 
than one item is not allowed as the second argument of concat() (2, 10, ...) 
2013-10-04 14:06:53,838 [ERROR] com.xmlcalabash.library.XSLT - A sequence of 
more than one item is not allowed as the second argument of concat() (2, 10, 
...) 
2013-10-04 14:06:53,843 [ERROR] com.xmlcalabash.library.XSLT - A sequence of 
more than one item is not allowed as the second argument of concat() (2, 10, 
...) 
2013-10-04 14:06:53,850 [DEBUG] org.daisy.pipeline.push.Poster - Status changed 
b5e57076-9c24-4d80-88b1-bdc3d30f28a0->DONE

What version of the product are you using? On what operating system?
v1.6-beta on Ubuntu Linux

Please provide any additional information below.
We are seeing this happening with quite a few of our DAISY books.

Original issue reported on code.google.com by john.bru...@gmail.com on 4 Oct 2013 at 9:29

Attachments:

b5e57076-9c24-4d80-88b1-bdc3d30f28a0.log

fatty- / daisy-pipeline

Error in DTBook conversion, "A sequence of more than one item is not allowed as the second argument of concat()" #368