IndexCopier$DeleteOldDirOnClose#close() should handle missing file

IndexCopier$DeleteOldDirOnClose#close() catches IOException, however, it uses FileUtils#sizeOf(File), which throws an IllegalArgumentException if the file does not exist.

22.07.2021 10:23:21.166 *WARN* [oak-lucene-5018] org.apache.jackrabbit.oak.plugins.index.lucene.LuceneIndexProviderService Error occurred in asynchronous processing 
java.lang.IllegalArgumentException: /path/to/repository/index/indexname-1626941798326/data does not exist
        at org.apache.commons.io.FileUtils.sizeOf(FileUtils.java:2541) [org.apache.commons.io:2.6.0]
        at org.apache.jackrabbit.oak.plugins.index.lucene.IndexCopier$DeleteOldDirOnClose.close(IndexCopier.java:468) [org.apache.jackrabbit.oak-lucene:1.22.4]
        at org.apache.jackrabbit.oak.plugins.index.lucene.directory.CopyOnReadDirectory$2.run(CopyOnReadDirectory.java:304) [org.apache.jackrabbit.oak-lucene:1.22.4]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)

The relevant block of code attempts to delete and old index directory. So skipping this if the directory does not exist seems appropriate.

Unfortunately the log files I analysed don't reach far back into the past, so I cannot say under which circumstances it can happen that the directory is already removed. What I know is that a few days later an out-of-disk situation was noticed, which was likely caused by repeated re-indexing runs. Furthermore, I have seen a SegmentNotFoundException for one specific segment. Once after a "successful" reindexing run (i.e. IndexUpdate reports "Reindexing completed"), during AsyncIndexUpdate#mergeWithConcurrencyCheck(). But most occurrences look like queries running into the missing segment.

Surely the issue described here is not the root-cause of the problem I am analysing. But at the very least it adds unnecessary noise.