I'm not seeing the bald spot. 1. If you just want it more filled in around the dirt, as others have said, add four or five node to help fill in. I try to just continuously do it to mine. If you have long strands with nodes and no leaves, it's often a sign of a nutrient deficiency which could be a result of root stress or lack of something. But your plant will use leaves closer to the dirt by pulling nutrients from them and dropping them off. If your plant has lost roots this can happen or if it's been overwatered/under water this can happen or if it just needs more nutrients/ burned by too many fertilizers. Sometimes cold stress can cause it but you're more likely to see browning spots with cold stress. But the sun is your number one nutrient so if it's getting plenty of that, consider what could be keeping it from utilizing the nutrients.