image objects with utf8 names chars disappear when caches are cleared.

0- Setup your site.ini with:
[URLTranslator]
TransformationGroup=urlalias_iri

also specify there your system's locale, for example:
[RegionalSettings]
SystemLocale=fr_FR.utf8

1- Create an image with name モンサーモンの and upload an image file.
2 - publish the object, and reopen it, select the view tab
3 - clear all caches with the button from the right toolbar
4 - image disappears.
with the debug active, an error from ezImageShellHandler::convert() shows up

5 - clear content cache from the menu (generic, node, subtree, is indifferent)
image appears again