Macro with empty parameter name produce bad result in xwiki/2.1 syntax

It seems that Confluence macros can have empty parameter name which current produces something like:

{{mymacro =""/}}

Unfortunately XWiki behavior does not make much sense currently with such content (see XRENDERING-601) so maybe the Confluence input filter should always set a name. For example, it uses "0" in the wiki syntax parser for the default parameter (it's mostly because parameters are not named in the wiki syntax but at least it would produce a consistent behavior).