Adobe released ACR 12.0 (Photoshop CC 2020). This update fixes several issues and adds support for new cameras and lenses. It also comes with a new feature -- Fill uneven edges in panoramas. According to the Help file, . . .
When you merge photos/HDR photos to create a panorama, select Fill Edges in the preview dialog box to automatically fill the uneven and transparent areas of your panorama/HDR panorama.