'Nothing happens' messages after drinking potion of extra healing

Two ‘nothing happens’ messages are often shown when these potions are drunk. The messages can be seen in the log on the bottom-right.

These messages also appear in the large overlay text that pops up initially after drinking the potion (which includes the normal text about being ‘greatly healed’), though I haven’t been able to get a screenshot of that, since pressing the screenshot button dismisses the popup.