### 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
if (tokenStream.hasAttribute(CharTermAttribute.class) == false
                    || tokenStream.hasAttribute(OffsetAttribute.class) == false) {
                    
                    continue;
                }
                TextFragment[] bestTextFragments = entry.getBestTextFragments(tokenStream, text, false, numberOfFragments);
                for (TextFragment bestTextFragment : bestTextFragments) {
                    if (bestTextFragment != null && bestTextFragment.getScore() > 0) {
                        fragsList.add(bestTextFragment);
                    }
                }
            } catch (BytesRefHash.MaxBytesLengthExceededException e) {
                
                
                
                
            } catch (InvalidTokenOffsetsException e) {
                throw new IllegalArgumentException(e);
            }
        }
        
        if (field.fieldOptions().scoreOrdered() == false) {
            CollectionUtil.introSort(fragsList, (o1, o2) -> o1.getFragNum() - o2.getFragNum());
        }
        String[] fragments;
        
        if (field.fieldOptions().numberOfFragments() == 0 && textsToHighlight.size() > 1 && fragsList.size() > 0) {
            fragments = new String[fragsList.size()];
            for (int i = 0; i < fragsList.size(); i++) {
                fragments[i] = fragsList.get(i).toString();