Kderusso/sparse vector ci failure (#117930)

* Fix CI failure in SparseVectorQueryBuilderTests

* Unmute test

Author: kderusso

muted-tests.yml

@@ -221,9 +221,6 @@ tests:
   issue: https://github.com/elastic/elasticsearch/issues/117815
 - class: org.elasticsearch.xpack.ml.integration.DatafeedJobsRestIT
   issue: https://github.com/elastic/elasticsearch/issues/111319
-- class: org.elasticsearch.xpack.core.ml.search.SparseVectorQueryBuilderTests
-  method: testToQuery
-  issue: https://github.com/elastic/elasticsearch/issues/117904
 - class: org.elasticsearch.packaging.test.ArchiveGenerateInitialCredentialsTests
   method: test20NoAutoGenerationWhenAutoConfigurationDisabled
   issue: https://github.com/elastic/elasticsearch/issues/117891

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/search/SparseVectorQueryBuilderTests.java

@@ -232,6 +232,12 @@ public void testToQuery() throws IOException {
 
     private void testDoToQuery(SparseVectorQueryBuilder queryBuilder, SearchExecutionContext context) throws IOException {
         Query query = queryBuilder.doToQuery(context);
+
+        // test query builder can randomly have no vectors, which rewrites to a MatchNoneQuery - nothing more to do in this case.
+        if (query instanceof MatchNoDocsQuery) {
+            return;
+        }
+
         assertTrue(query instanceof SparseVectorQueryWrapper);
         var sparseQuery = (SparseVectorQueryWrapper) query;
         if (queryBuilder.shouldPruneTokens()) {