Thumbnail or preview of files whose name is non-ascii and extension is JPG is corrupted

Issue Summary

If attachment has a non-ascii name and JPG extension (e.g. テスト.JPG), the image of thumbnail or preview is corrupted and unviewable.

Environment

Version 6.6.14

Steps to Reproduce

1. Go to a Confluence page.
2. Click Tools >> Attachment
3. Click Choose File button
4. Attach file with the name テスト.jpg

Expected Results

Thumbnail is shown in the editor and the published page.

Actual Results

The attached file is corrupted and cannot be viewed.

The below exception is thrown in the atlassian-confluence.log file:

2019-07-31 06:47:31,919 ERROR [http-nio-8090-exec-3] [[Standalone].[localhost].[/].[file-server]] log Servlet.service() for servlet [file-server] in context with path [] threw exception
java.lang.NullPointerException
	at com.atlassian.confluence.image.effects.ImageFilterServlet.buildAttachmentContext(ImageFilterServlet.java:231)
	at com.atlassian.confluence.image.effects.ImageFilterServlet.doGetInTransaction(ImageFilterServlet.java:146)
	...

Notes

• This error is NOT observed in version 6.6.13
• Apparently this was fixed by CONFSERVER-31088. And this error is NOT observed in version 6.13.x and later.

Workaround

Either of follows.

• Use .jpeg for the file extension instead of .jpg.
• Upgrade to 6.7.2 or later which include the fix of CONFSERVER-31088