BetterRaidFrames

Bug fixes:
- Attempt to fix a rare bug that caused a lua error when clicking Ready/Not Ready during ready checks
- Fix a bug that caused all ready check icons to reset when a member disconnected or changed roles during a ready check.
- Fix a bug that caused an incorrect message to show for offline members after a ready check.
- Fix some issues that caused the opacity to flicker in some cases when using the fade when out-of-range option. (Where possible, at the moment not possible to 100% fix this)

- Generally improved Offline detection during ready checks. If someone goes offline during a ready check, they're automatically marked as not ready. If they come back online, their old ready status is restored.