Currently playing on Classic beta, get this error from time to time:

Message: Interface\AddOns\Kui_Nameplates\elements/castbar.lua:107: attempt to call global 'UnitCastingInfo' (a nil value)
Time: Tue Jun 11 13:54:45 2019
Count: 3
Stack: Interface\AddOns\Kui_Nameplates\elements/castbar.lua:107: attempt to call global 'UnitCastingInfo' (a nil value)
Interface\AddOns\Kui_Nameplates\elements/castbar.lua:107: in function Show' Interface\AddOns\Kui_Nameplates\elements/castbar.lua:173: in function EnableOnFrame'
Interface\AddOns\Kui_Nameplates\nameplate.lua:55: in function EnableElement' Interface\AddOns\Kui_Nameplates_Core\create.lua:1186: in function UpdateCastBar'
Interface\AddOns\Kui_Nameplates_Core\create.lua:2095: in function NameOnlyUpdateFunctions' Interface\AddOns\Kui_Nameplates_Core\hook.lua:122: in function func'
Interface\AddOns\Kui_Nameplates\messages.lua:129: in function DispatchMessage' Interface\AddOns\Kui_Nameplates\elements/target.lua:9: in function <Interface\AddOns\Kui_Nameplates\elements/target.lua:7> Interface\AddOns\Kui_Nameplates\elements/target.lua:29: in function func'
Interface\AddOns\Kui_Nameplates\messages.lua:166: in function <Interface\AddOns\Kui_Nameplates\messages.lua:146>
Interface\AddOns\Kui_Nameplates\messages.lua:219: in function <Interface\AddOns\Kui_Nameplates\messages.lua:213>
[C]: in function `TurnOrActionStop'
[string "TURNORACTION"]:4: in function <[string "TURNORACTION"]:1>

Locals: self =

{
DisableOnFrame = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:176
Enable = defined @interface\AddOns\Kui_Nameplates\messages.lua:499
HIDE_SUCCESS = 3
priority = 0
HIDE_FRAME = 0
enabled = true
CastStart = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:121
UNIT_SPELLCAST_CHANNEL_STOP = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:166
HIDE_INTERRUPT = 1
CastUpdate = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:148
enable_on_load = true
element = true
Show = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:106
CastStop = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:141
name = "CastBar"
EnableOnFrame = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:171
Hide = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:117
Create = defined @interface\AddOns\Kui_Nameplates\elements/castbar.lua:98
HIDE_STOP = 2
Disable = defined @interface\AddOns\Kui_Nameplates\messages.lua:508
}
f = KuiNamePlate8 {
LevelText = {
}
Highlight = {
}
UpdateMainBars = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:455
parent = NamePlate8 {
}
UpdateHealthText = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:701
UpdateRaidIcon = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:1521
UpdateFrameGlow = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:832
bg = {
}
UpdateGuildText = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:743
unit = "nameplate1"
UpdateLevelText = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:651
TargetGlow = {
}
ThreatGlow = {
}
state = {
}
UpdateNameOnlyGlowSize = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:2067
ShowCastBar = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:1055
NameOnlyGlow = {
}
RaidIcon = {
}
0 =
UpdateStateIcon = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:1483
UpdateFrameSize = defined @interface\AddOns\Kui_Nameplates_Core\create.lua:383
ThreatBrackets = {
}
SpellIcon = {
}
elements = {
}
HealthText = {
}
StateIcon = {
}
handler = {
}
CastBar = {
}
UpdateAuras = defined @interface\AddOns\Kui_N