TermOrdsIterator#lookup throws ArrayIndexOutOfBoundsException [LUCENE-3377]

TermOrdsIterator's lookup method can throw an ArrayIndexOutOfBoundsException if reuse argument is reused acros segments.

Example collector:

```Java
private DocTermOrds.TermOrdsIterator reuse = null;

public void collect(int doc) throws IOException {
...
reuse = docTermOrds.lookup(doc, reuse);
...
}

public void setNextReader(IndexReader.AtomicReaderContext context) throws IOException {
docTermOrds = FieldCache.DEFAULT.getDocTermOrds(context.reader, field);
....
}
```

If reuse argument is always null exception doesn't occur.

---
Migrated from [LUCENE-3377](https://issues.apache.org/jira/browse/LUCENE-3377) by Martijn van Groningen (@martijnvg), updated Aug 17 2011

Start at DocTermOrds.TermOrdsIterator#lookup and inspect the collector example, especially reuse across IndexReader segments in setNextReader. Reproduce the failure with a reused iterator and verify that the example no longer throws ArrayIndexOutOfBoundsException; the issue does not name a specific test or file.

Written by the indexing model from the issue text.