### Environment:
Elasticsearch version:
```
{
    "number" : "7.15.0",
    "build_flavor" : "default",
    "build_type" : "zip",
    "build_hash" : "79d65f6e357953a5b3cbcc5e2c7c21073d89aa29",
    "build_date" : "2021-09-16T03:05:29.143308416Z",
    "build_snapshot" : false,
    "lucene_version" : "8.9.0",
    "minimum_wire_compatibility_version" : "6.8.0",
    "minimum_index_compatibility_version" : "6.0.0-beta1"
}
```
Plugins installed: []
JVM version :1.8
OS version :Windows 10

### Steps to reproduce:
```
PUT test_plain_highlighter 
{}

POST /test_plain_highlighter/_doc/1
{
  "description": [
    "Lorem Ipsum string Generator that helps to create dummy text for all layout needs.",
    "It has roots in a piece of classical Latin literature from 45 BC, making it search string over 2000 years old."
  ]
}

POST /test_plain_highlighter/_search
{
  "highlight": {
    "order": "score",
    "type": "plain",
    "fields": {
      "*": {}
    },
    "fragment_size": 50
  },
  "query": {
    "match": {
      "description": "search string"
    }
  },
  "_source": ""
}
```

### RECEIVED Highlighted Fragment in response:
```
[
   "Lorem Ipsum <em>string</em> Generator that helps to create",
   " literature from 45 BC, making it <em>search</em> <em>string</em> over 2000 years old."
]
```
### EXPECTED Highlighted Fragment:
```
[
   " literature from 45 BC, making it <em>search</em> <em>string</em> over 2000 years old.",
   "Lorem Ipsum <em>string</em> Generator that helps to create"
]
```
server/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/PlainHighlighter.java
}
        } else {
            
            numberOfFragments = Math.min(fragsList.size(), numberOfFragments);
            fragments = new String[numberOfFragments];
            for (int i = 0; i < fragments.length; i++) {
                fragments[i] = fragsList.get(i).toString();
            }
        }
        if (fragments.length > 0) {
            return new HighlightField(fieldContext.fieldName, Text.convertFromStringArray(fragments));
        }
        int noMatchSize = fieldContext.field.fieldOptions().noMatchSize();
        if (noMatchSize > 0 && textsToHighlight.size() > 0) {
            
            String fieldContents = textsToHighlight.get(0).toString();
            int end = findGoodEndForNoHighlightExcerpt(noMatchSize, analyzer, fieldType.name(), fieldContents);
            if (end > 0) {
                return new HighlightField(fieldContext.fieldName, new Text[] { new Text(fieldContents.substring(0, end)) });
            }
        }
        return null;
    }
    @Override
    public boolean canHighlight(MappedFieldType fieldType) {
        return true;
    }
    private static int findGoodEndForNoHighlightExcerpt(int noMatchSize, Analyzer analyzer, String fieldName, String contents)
        throws IOException {
        try (TokenStream tokenStream = analyzer.tokenStream(fieldName, contents)) {