No, microwave radiation will not damage the glass in a microwave oven if it's left on without anything inside it. Microwave ovens are designed to contain the microwave radiation safely within the cooking chamber. The glass door and metal mesh screen on the front of the microwave are designed to prevent the microwaves from escaping outside the oven.
When you operate a microwave oven without any food or other items inside, the microwave energy is simply reflected back and forth within the oven cavity. This is why it is not advisable to run a microwave empty for an extended period of time, as it can lead to a buildup of heat inside the oven, potentially causing damage to the microwave's internal components.
To ensure the safe and proper operation of your microwave oven, always use it with food or microwave-safe containers inside the cooking chamber. If you accidentally turn on the microwave without anything inside, it is generally safe for short periods, but it's best to turn it off quickly and avoid prolonged operation without any contents.