Happens upon every mouseover of another player. Using TipTac and the TipTac Reborn update for it.

73x totalRP3/Libs/LibMSP/LibMSP.lua:750: Chomp.NameMergedRealm: name: expected string, got nil
[string "=[C]"]: in function error' [string "@totalRP3/Libs/Chomp/StringManip.lua"]:104: in function NameMergedRealm'
[string "@totalRP3/Libs/LibMSP/LibMSP.lua"]:750: in function Request' [string "@TipTac/ttCore.lua"]:2171: in function SetUnitRecordFromTip'
[string "@TipTac/ttCore.lua"]:2327: in function ?' [string "@TipTac/libs/LibFroznFunctions-1.0-2/LibFroznFunctions-1.0.lua"]:688: in function FireGroupEvent'
[string "@TipTac/ttCore.lua"]:1174: in function SetCurrentDisplayParams' [string "@TipTac/ttCore.lua"]:1086: in function <TipTac/ttCore.lua:1085> [string "@TipTac/libs/LibFroznFunctions-1.0-2/LibFroznFunctions-1.0.lua"]:137: in function <...libs/LibFroznFunctions-1.0/LibFroznFunctions-1.0.lua:135> [string "=(tail call)"]: ? [string "=[C]"]: in function securecallfunction'
[string "@SharedXML/Tooltip/TooltipDataHandler.lua"]:60: in function <SharedXML/Tooltip/TooltipDataHandler.lua:55>
[string "@SharedXML/Tooltip/TooltipDataHandler.lua"]:80: in function <SharedXML/Tooltip/TooltipDataHandler.lua:76>
[string "@SharedXML/Tooltip/TooltipDataHandler.lua"]:116: in function <SharedXML/Tooltip/TooltipDataHandler.lua:106>
[string "=[C]"]: in function SetAttribute' [string "@SharedXML/Tooltip/TooltipDataHandler.lua"]:141: in function <SharedXML/Tooltip/TooltipDataHandler.lua:134> [string "@SharedXML/Tooltip/TooltipDataHandler.lua"]:278: in function <SharedXML/Tooltip/TooltipDataHandler.lua:236> [string "=[C]"]: in function securecallfunction'
[string "@SharedXML/Tooltip/TooltipDataHandler.lua"]:233: in function ProcessInfo' [string "@FrameXML/GameTooltip.lua"]:970: in function SetWorldCursor'
[string "@FrameXML/UIParent.lua"]:1486: in function <FrameXML/UIParent.lua:1409>
[string "=[C]"]: ?

Locals:
(*temporary) = "Chomp.NameMergedRealm: name: expected string, got nil"

This is TipTac's problem - they'll be releasing an update eventually to resolve it.

Wow, fast response. And understood. Thanks!

For what it's worth - there is a development version of TipTac with the fix included, if the issue is annoying enough: frozn/TipTac#173 (comment)