[Torhal]

You need to do a check like this:

MySV = MySV or {}

This uses the pre-existing SVs or creates an empty table if there are none.

You can also improve your slashcmdhandler like this:

local COMMAND_PARAMS = {
    hide = function()
        if TXPVisible then
            TXPVisible=false
            TribalExperienceBar:Hide() 
            print("Experience hidden, type /TXP show to show.")
        end
    end,
    show = function()
        if not TXPVisible then
            TXPVisible=true
            TribalExperienceBar:Show()
            print("Experience displayed, type /TXP hide to hide.")
        end
    end,
    rested = function()
        if GetXPExhaustion() == nil then
            print("You have no rested EXP.")
        else
            print("You have "..GetXPExhaustion().." rested EXP remaining.")
        end
    end,
    lock = function()
        if TXPLocked == true then
            TXPLocked = false
            print("TXP UNlocked")
        elseif TXPLocked == false then
            TXPLocked = true
           print("TXP Locked")
        end 
    end,
    curve = function()
        if TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\curve") == true then
            TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\curve")
            print("Texture already set to Curve")
        elseif TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\curve") == false then
            TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\curve")
            print("Texture set to Curve")
        end
    end,
    simple = function()
        if TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\simple") == true then
            TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\simple")
            print("Texture already set to Simple")
        elseif TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\simple") == false then
            TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\simple")
            print("Texture set to Simple")
        end
    end,
    split = function()
        if TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\split") == true then
            TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\split")
            print("Texture already set to Split")
        elseif TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\split") == false then
            TribalExperienceBar:SetStatusBarTexture("Interface\\AddOns\\TXP\\media\\split")
            print("Texture set to Split")
        end 
    end,    
}
 
local function slashcmdhandler(param)
    if COMMAND_PARAMS[param] then
        COMMAND_PARAMS[param]()
        return
    end
    print("Valid commands are:");
    print("/TXP show (Show the experience bar.)");
    print("/TXP hide (Hide the experience bar.)");
    print("/TXP rested (Shows the amount of rested XP.)");
    print("/TXP Lock (Locks the experience bar if it is unlocked, Unlocks it if it is locked.")
    print("/TXP Curve (Sets the status bar texture to Curve.")
    print("/TXP Simple (Sets the bar texture to Simple")
    print("/TXP Split (Sets the Bar texture to Split")
end

This works by doing a simple table lookup and quickly coming back with a result or nil, instead of testing each check in an if-else chain.