MediaWikiInputFilterStream#toEntityReference can fail due to a bad reference

MediaWikiInputFilterStream#toEntityReference should return a corresponding entity reference from the a provided MediaWiki reference. However, there are some cases where this method can fail unexpectedly, as it tries to create an entity reference with an empty name (which is impossible and will throw an IllegalArgumentException).
This is the case when the provided reference is in the form of "MySpace:" (no page name)

Such exception will actually make the filter fail altogether, and if an import is performed form mediawiki to XWiki using the filter stream application in XWiki, the import will fail.