"You aren't in a party" is repeated over and over

This error happens when in a Dungeon Finder group.

10x [ADDON_ACTION_BLOCKED] AddOn 'Bartender4' tried to call the protected function 'UNKNOWN()'.
[string "@!BugGrabber/BugGrabber.lua"]:481: in function <!BugGrabber/BugGrabber.lua:481>
[string "=[C]"]: ?
[string "@Bartender4/libs/LibWindow-1.1-18/LibWindow-1.1.lua"]:178: in function `RestorePosition'
[string "@Bartender4/Bar.lua"]:313: in function `LoadPosition'
[string "@Bartender4/Bar.lua"]:238: in function `ApplyConfig'
[string "@Bartender4/BlizzardArt.lua"]:156: in function `ApplyConfig'
[string "@Bartender4/BlizzardArt.lua"]:129: in function <Bartender4/BlizzardArt.lua:128>
[string "=(tail call)"]: ?
[string "=[C]"]: in function `MainMenuBar_UpdateKeyRing'
[string "@FrameXML/MainMenuBar.lua"]:108: in function <FrameXML/MainMenuBar.lua:89>