In some cases where a user offers a bounty and then is deleted, it seems Community becomes the owner of the bounty. If the bounty was started with a bounty notice, the revision history no longer has anyone to attribute the addition/removal of that notice to, leading to a broken message like might happen on the award icon when a user is merged.
Looking at a revision history where this happens, you can see that the only history entry where the notice action was attributed to Community was the removal of the first bounty notice, due to the fact that the bounty was ended automatically.
Since the offering of the bounty itself is listed as being performed by Community, the notice should either behave the same way, or drop the "by" in cases where the owner can no longer be referenced.
