The United Nations and aid groups have warned of grave consequences for Yemen after an international pledging conference failed to raise enough money to prevent a humanitarian catastrophe in the war-torn country. Overshadowed by the conflict in Ukraine, aid-starved Yemen – already suffering the world’s worst humanitarian crisis, according to the UN – is on the verge of total collapse. With the country almost completely dependent on imports, aid groups say the situation will only worsen following Russia’s invasion of Ukraine, which produces nearly a third of Yemeni wheat supplies. Some 80 perce…