"this.stopWords" is null

[Thomas Woodard]

I had an 8.11.1 implementation in progress when 9.0 came out, and am trying
to convert it so we don't go live on an already outdated version. I'm
having trouble adding documents to the index that worked fine with 8.11.1.
Shortened error is below:

2022-06-07 13:49:24.190 ERROR (qtp554868511-21) [ x:sku]
o.a.s.h.RequestHandlerBase org.apache.solr.common.SolrException: Exception
writing document id 6-1-TB-0701 to the index; possible analysis error. =>
org.apache.solr.common.SolrException: Exception writing document id
6-1-TB-0701 to the index; possible analysis error.
Caused by: java.lang.NullPointerException: Cannot invoke
"org.apache.lucene.analysis.CharArraySet.contains(char[], int, int)"
because "this.stopWords" is null
        at org.apache.lucene.analysis.StopFilter.accept(StopFilter.java:97)
~[?:?]
        at
org.apache.lucene.analysis.FilteringTokenFilter.incrementToken(FilteringTokenFilter.java:52)
~[?:?]
        at
org.apache.lucene.analysis.LowerCaseFilter.incrementToken(LowerCaseFilter.java:37)
~[?:?]
        at
org.apache.lucene.index.IndexingChain$PerField.invert(IndexingChain.java:1142)
~[?:?]
        at
org.apache.lucene.index.IndexingChain.processField(IndexingChain.java:729)
~[?:?]
        at
org.apache.lucene.index.IndexingChain.processDocument(IndexingChain.java:620)
~[?:?]
        at
org.apache.lucene.index.DocumentsWriterPerThread.updateDocuments(DocumentsWriterPerThread.java:239)
~[?:?]
        at
org.apache.lucene.index.DocumentsWriter.updateDocuments(DocumentsWriter.java:432)
~[?:?]
        at
org.apache.lucene.index.IndexWriter.updateDocuments(IndexWriter.java:1530)
~[?:?]
        at
org.apache.lucene.index.IndexWriter.updateDocuments(IndexWriter.java:1519)
~[?:?]
        at
org.apache.solr.update.DirectUpdateHandler2.updateDocOrDocValues(DirectUpdateHandler2.java:1046)
~[?:?]
        at
org.apache.solr.update.DirectUpdateHandler2.doNormalUpdate(DirectUpdateHandler2.java:416)
~[?:?]
        at
org.apache.solr.update.DirectUpdateHandler2.addDoc0(DirectUpdateHandler2.java:369)
~[?:?]
        at
org.apache.solr.update.DirectUpdateHandler2.addDoc(DirectUpdateHandler2.java:300)
~[?:?]
        ... 80 more

I have double checked all the stop filters in my schema.xml in my
configset, and they all seem fine. The import should only be using
text_general, which is configured like this:
   <fieldType name="text_general" class="solr.TextField"
positionIncrementGap="100" multiValued="true">
      <analyzer type="index">
        <tokenizer name="standard"/>
        <filter name="stop" ignoreCase="true" words="./stopwords.txt" />
        <!-- in this example, we will only use synonyms at query time
        <filter name="synonymGraph" synonyms="index_synonyms.txt"
ignoreCase="true" expand="false"/>
        <filter name="flattenGraph"/>
        -->
        <filter name="lowercase"/>
      </analyzer>
      <analyzer type="query">
        <tokenizer name="standard"/>
        <filter name="stop" ignoreCase="true" words="./stopwords.txt" />
        <filter name="synonymGraph" synonyms="./synonyms.txt"
ignoreCase="true" expand="true"/>
        <filter name="lowercase"/>
      </analyzer>
    </fieldType>

I can't figure out what the problem is, or how to do more detailed
debugging to find it. Any help would be greatly appreciated.