On Retail, using the latest version of EME, upon logging in:

4x ...d/libs/EditModeExpanded-1.0-24/EditModeExpanded-1.0.lua:562: attempt to index field 'settings' (a nil value)
[string "@EditModeExpanded/libs/EditModeExpanded-1.0-24/EditModeExpanded-1.0.lua"]:562: in function `func'
[string "@EditModeExpanded/libs/EditModeExpanded-1.0-24/EditModeExpanded-1.0.lua"]:1032: in function <...d/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:942>

Locals:
db =

{
}
(*temporary) = nil
(*temporary) = 12
(*temporary) = "attempt to index field 'settings' (a nil value)"
framesDB = {
13 = {
}
15 = {
}
3 = {
}
14 = {
}
16 = {
}
}
frame = CompactRaidFrameContainer {
0 =
GetUnitFrame = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:315
UpdateMagnetismRegistration = defined @FrameXML/EditModeSystemTemplates.lua:506
GetSnapOffsets = defined @FrameXML/EditModeSystemTemplates.lua:411
systemInfo = {
}
IsFrameAnchoredToMe = defined @FrameXML/EditModeSystemTemplates.lua:469
ApplyToFrames = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:115
SetFlowSortFunction = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:89
SetBorderShown = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:110
ReadyToUpdate = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:132
ResetToDefaultPosition = defined @FrameXML/EditModeSystemTemplates.lua:148
GetScaledSelectionSides = defined @FrameXML/EditModeSystemTemplates.lua:355
displayPets = true
SelectSystem = defined =[C]:-1
GetFrameMagneticEligibility = defined @FrameXML/EditModeSystemTemplates.lua:489
UpdateSystemSettingUseLargerFrame = defined @FrameXML/EditModeSystemTemplates.lua:971
AddLayoutChildren = defined @SharedXML/LayoutFrame.lua:48
IsBelowFrame = defined @FrameXML/EditModeSystemTemplates.lua:322
SetScaleBase = defined =[C]:-1
HasActiveChanges = defined @FrameXML/EditModeSystemTemplates.lua:244
AddFlaggedUnits = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:274
flowFilterFunc = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameManager.lua:523
EMEanchorTo = UIParent {
}
DoesSettingDisplayValueEqual = defined @FrameXML/EditModeSystemTemplates.lua:268
OnLoad = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:14
Layout = defined @SharedXML/LayoutFrame.lua:333
settingDisplayInfoMap = {
}
GetSettingValueBool = defined @FrameXML/EditModeSystemTemplates.lua:259
TryUpdate = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:126
OnSizeChanged = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:63
DoesSettingValueEqual = defined @FrameXML/EditModeSystemTemplates.lua:263
MarkDirty = defined @SharedXML/LayoutFrame.lua:90
UpdateSelectionVerticalState = defined @FrameXML/EditModeSystemTemplates.lua:1084
AddUnitFrame = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:303
AddPets = defined @Blizzard_CompactRaidFrames/Blizzard_CompactRaidFrameContainer.lua:251
dirtySettings = {
}
IsToTheLeftOfFrame = defined @FrameXML/EditModeSystemTemplates.lua:304
GetSettingsDialogAnchor = defined @FrameXML/EditModeSystemTemplates.lua:288
hasActiveChanges = false
OnSystemLoad = defined @FrameXML/EditModeSystemTemplates.lua:3
ClearFrameSnap = defined @FrameXML/EditModeSystemTemplates.lua:448
GetCombinedCenterOffset = defined @FrameXML/EditModeSystemTemplates.lua:398
SetupSettingsDialogAnchor = defined @FrameXML/EditModeSystemTemplates.lua:948
UpdateSystemSettingSortPla

Unfortunately, this seems to still be lurking around in a slightly different format. I am getting it on my mage every time I "zone in" after a teleport/portal spell OR traveling via normal in game portals.

5x ...d/libs/EditModeExpanded-1.0-24/EditModeExpanded-1.0.lua:561: attempt to index field 'settings' (a nil value)
[string "@EditModeExpanded/libs/EditModeExpanded-1.0-24/EditModeExpanded-1.0.lua"]:561: in function `IsFrameMarkedHidden'
[string "@EditModeExpanded/EditModeExpanded.lua"]:281: in function <EditModeExpanded/EditModeExpanded.lua:280>
[string "=[C]"]: ?

Locals:
self =

{
RegisterMinimapPinnable = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:1087
RegisterHideable = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:543
RegisterFrame = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:152
SetDefaultSize = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:478
IsFrameEnabled = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:577
RepositionFrame = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:494
IsFrameMarkedHidden = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:558
RegisterResizable = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:521
IsRegistered = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:569
SetDontResize = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:487
RegisterCustomCheckbox = defined @EditModeExpanded/libs/EditModeExpanded-1.0/EditModeExpanded-1.0.lua:585
}
frame = TalkingHeadFrame {
0 =
OnPostShow = defined @FrameXML/AlertFrameIntrinsic.lua:4
SetExternallyManagedOutroAnimation = defined @FrameXML/AlertFrameIntrinsic.lua:28
UpdateMagnetismRegistration = defined @FrameXML/EditModeSystemTemplates.lua:506
GetSnapOffsets = defined @FrameXML/EditModeSystemTemplates.lua:411
GetSettingValue = defined @FrameXML/EditModeSystemTemplates.lua:252
systemInfo = {
}
GetCombinedSelectionOffset = defined @FrameXML/EditModeSystemTemplates.lua:387
ClearAllPointsBase = defined =[C]:-1
isClosing = false
isBottomManagedFrame = true
OnShow = defined @FrameXML/UIParent.lua:2461
dirtySettings = {
}
OnDragStop = defined @FrameXML/EditModeSystemTemplates.lua:574
layoutParent = UIParentBottomManagedFrameContainer {
}
settingMap = {
}
UpdateSystemSettingValue = defined @FrameXML/EditModeSystemTemplates.lua:131
GetSelectionOffset = defined @FrameXML/EditModeSystemTemplates.lua:363
IsVerticallyAlignedWithFrame = defined @FrameXML/EditModeSystemTemplates.lua:328
FadeinFrames = defined @FrameXML/TalkingHeadUI.lua:57
ResetToDefaultPosition = defined @FrameXML/EditModeSystemTemplates.lua:148
ConvertSettingDisplayValueToRawValue = defined @FrameXML/EditModeSystemTemplates.lua:95
ShouldShowSetting = defined @FrameXML/EditModeSystemTemplates.lua:284
SetSnappedToFrame = defined @FrameXML/EditModeSystemTemplates.lua:437
SelectSystem = defined =[C]:-1
savedSystemInfo = {
}
OnManagedAlertFrameVisibilityChanged = defined @FrameXML/AlertFrameIntrinsic.lua:20
GetFrameMagneticEligibility = defined @FrameXML/EditModeSystemTemplates.lua:489
ClearDirtySetting = defined @FrameXML/EditModeSystemTemplates.lua:127
IsInitialized = defined @FrameXML/EditModeSystemTemplates.lua:227
UpdateSystemSetting = defined @FrameXML/EditModeSystemTemplates.lua:213
SetAlertContainer = defined @FrameXML/AlertFrameIntrinsic.lua:12
EMESystemID = 16
NameFrame = Frame {
}
EMEanchorTo = UIParent {
}
IsBelowFrame = defined @FrameXML/EditModeSystemTemplates.lua:322
RemoveSnappedFrame = defined @FrameXML/EditModeSystemTemplates.lua:427