LONDON—British Prime Minister Boris Johnson said he had called a virtual G-7 leaders’ meeting for Tuesday to discuss the crisis in Afghanistan and urged governments to find ways to prevent conditions from getting worse. Taliban terrorists seized control of Kabul last weekend in an upheaval that sent civilians and Afghan military allies fleeing for safety. Many fear a return to the austere interpretation of Islamic law imposed during the previous Taliban rule that ended 20 years ago. Western governments are discussing how to handle the situation in Kabul where thousands of civilians desperate to flee have descended on the airport. “It is vital that the international community works together to ensure safe evacuations, prevent a humanitarian crisis, and support the Afghan people to secure the gains of the last 20 years,” Johnson said on Twitter on Sunday. Britain holds the rotating leadership of the G-7, which also includes the United …