solrdedup crashes if digest-field not compiled

[Matthias Paul]

Hi,

if I run bin/nutch solrdedup <SOLR_URL> it crashes with
java.lang.NullPointerException
    at org.apache.hadoop.io.Text.encode(Text.java:388)
    at org.apache.hadoop.io.Text.set(Text.java:178).

I suppose this happens because in my solr-index there are not only documents
from nutch but also from a database. So not all records have the
digest-field compiled.
What can I do?
Isn't there the possibility to override the query which Nutch sends to Solr
id:[* TO *]?

Thanks
Matthias