Completion postings format: Write hole character

Another issue found by randomized testing.

src/main/java/org/elasticsearch/search/suggest/completion/AnalyzingCompletionLookupProvider.java

@@ -159,6 +159,7 @@ public class AnalyzingCompletionLookupProvider extends CompletionLookupProvider
                             output.writeVInt(XAnalyzingSuggester.SEP_LABEL);
                             output.writeVInt(XAnalyzingSuggester.END_BYTE);
                             output.writeVInt(XAnalyzingSuggester.PAYLOAD_SEP);
+                            output.writeVInt(XAnalyzingSuggester.HOLE_CHARACTER);
                         }
                     }
                 };