Using appExec for the last application that registered the document was failing
in certain cases, such as for the Open Office for which the application
execution string is being registered as "soffice %u" in ~/.recently-used.xbel.
In general, using the default application for the mime type seems to be a more
predictable way to open documents. We still fall back to using the appExect
for the last application if the default application for a given mime type was
not found.
d67c88e4dc