I have groups for each race and class, so I can have mount selections for each of them.
Today I was adding the first D.R.I.V.E. mount to all my groups, and every time I added it it gave me this Lua error.
The functionality of the addon was not impaired.
Running the latest CurseForge release at the time of writing.

37x LiteMount/UI/Groups.lua:255: attempt to index field 'Mounts' (a nil value)
[LiteMount/UI/Groups.lua]:255: in function <LiteMount/UI/Groups.lua:247>

Locals:
self = Button {
BottomLeftCorner = Texture {
}
backdropBorderColor =

{
}
TopLeftCorner = Texture {
}
Checked = Texture {
}
mount = {
}
TopRightCorner = Texture {
}
Center = Texture {
}
RightEdge = Texture {
}
TopEdge = Texture {
}
backdropInfo = {
}
BottomEdge = Texture {
}
CheckBox = Texture {
}
BottomRightCorner = Texture {
}
Name = FontString {
}
LeftEdge = Texture {
}
}
group = "BloodElf"
(*temporary) = nil
(*temporary) = nil
(*temporary) = {
flags = {
}
name = "G-99 Breakneck"
family = "None"
icon = 4200126
spellID = 1215279
}
(*temporary) = "BloodElf"
(*temporary) = "attempt to index field 'Mounts' (a nil value)"
LM = {
C_Spell = {
}
TravelForm = {
}
Mount = {
}
Drive = {
}
FLAG = {
}
MountRegistry = Frame {
}
MountList = {
}
Spell = {
}
UIFilter = {
}
ActionButton = {
}
Actions = {
}
RuleSet = {
}
Rule = {
}
Journal = {
}
Options = {
}
RuleArguments = {
}
Vars = {
}
Conditions = {
}
Nagrand = {
}
RunningWild = {
}
SPELL = {
}
MOUNT_TYPE_NAMES = {
}
Soar = {
}
GhostWolf = {
}
db = {
}
SecureAction = {
}
RuleContext = {
}
RuleBoolean = {
}
Environment = Frame {
}
MOUNTFAMILY_BY_SPELL_ID = {
}
MOUNTFAMILY = {
}
C_MountJournal = {
}
ITEM = {
}
MOUNT_TYPE_INFO = {
}
Localize = {
}
ItemSummoned = {
}
}