Native v8.1.2

This release fixes several UI issues including empty message previews during app updates, an inoperable "Customize" button after certain navigation sequences, and a layout problem when editing gallery links.

• Fixes an issue where long-running message fetching on app update would cause the app to show "No posts" in group/channel message previews.
• Fixes an issue where tapping "Customize" in a new group, then navigating to the Group Settings & Info screen, then navigating back to the empty channel would cause the "Customize" button to be inoperable.
• Fixes an issue where editing a Link item in a gallery would cause a screen layout mishap.