This is a strange bug but when a potion effect is applied in creative mode and your taking a chest out of the creative menu a black bar appears. This only works with Chest, Trapped Chest and Ender Chest from what I tested.
- Be In creative
- Apply an effect (Any will Do)
- Look up chest in creative inventory
- grab Chest, Ender Chest or Trapped Chest (Only grab one because grabbing 2 fixes it)
I provided an Image down below
Update: It also works with Banners and Beds (Any Color)