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R759853, 762232 drop entity Port_Let_PortLet_Category and Portlet_Category portal_page_column, portal_page_portlet and portal_page and reload these from seed data.
R765862: any users which have the theme set in userPreferences set to "DEFAULT", the record should be deleted.
R766426
alter table WEB_SITE drop VISUAL_THEME_SET
drop table Visual_Theme_Resource, Visual_Theme,VISUAL_THEME_SET
and then reload from seed data
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execute an ant run-install-seed
RNot Sure which revision but the "DEFAULT"