I don't reproduce.
My theory is that this.validaton could be null for some reason there, but I don't know why this would happen.
https://github.com/xwiki-contrib/confluence/blob/8acffc85480f306aae1366fcfac7f9a7daee7cfe/confluence-xml/src/main/java/org/xwiki/contrib/confluence/filter/internal/input/XWikiConverter.java#L65
Thomas Mortagne do you know why we don't use @Inject for this field?
