Rob Kardashian hinted that he may suffer from erectile dysfunction during a rare appearance on this week’s episode of The Kardashians, RadarOnline.com has learned. The Daily Mail reports that Rob made the shocking revelation while discussing, and ultimately turning down, the prospect of donating sperm to Khloé Kardashian’s friend Malika Haqq. Malika, who is currently a single mother to her 3-year-old son Ace, opened up to Khloé about wanting another child and revealed that she was considering going to a sperm bank. “Why don’t you just ask Rob to give you some sperm? He’s a good catch. You guys…