dubai crown prince abu dhabi offer condolences son slay former yemen president ali abdullah saleh residence abu dhabi accord official twitter account account tweet picture sheikh mohammed bin zayed al-nahyan crown prince abu dhabi deputy supreme commander uae arm force visit ahmed ali residence unite arab emirates capital ahmed ali former commander yemen elite republican guard serve yemen ambassador uae join ally saudi arabia make war houthis abu dhabi crown prince offer condolences exile son slay yemeni ex-leader uae