Boss health bars show up when loading The End

When entering 'The End' boss health bars show for a few seconds upon loading. This is not my first time to 'The End' as the Ender dragon has already been defeated.

Steps to reproduce

• Go to 'The End' (Dragon must be alive)
• Kill everything with /kill @e or just defeat the dragon normally.
• Return to the overworld.
• Go back to 'The End' again and you'll always see boss health bars for a few seconds upon loading the end even though no dragon boss or wither bosses exist.