Fix handling of gnucash.appdata.xml

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23768 57a11ea4-9604-0410-9ed3-97b8803252fd
Release 2.6.1

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23769 57a11ea4-9604-0410-9ed3-97b8803252fd