SYDNEY, Jan 16 (Reuters) - An Australian court upheld a government decision to cancel Novak Djokovic"s visa on Sunday, ending the unvaccinated tennis superstar"s hopes of winning the Australian Open and racking up a record-breaking 21 men"s Grand Slam titles. Ruling on a case that has gripped Australia and the sporting world for more than a week, a three-judge bench of the Federal Court heard government lawyers arguments that Djokovic"s continued presence risked whipping up anti-vaccination sentiment during Australia"s worst outbreak of COVID-19 since the pandemic began. A medical exemption that allowed the Serbian tennis world number one to enter the country without being vaccinated had sparked fury in Australia, and became a political issue for Prime Minister Scott Morrison, who has to call a federal election before May.