Check if debuff exists in game

[MaLarsson]

As the title says, I need help with error control.
The player types in the name of a debuff and if this debuff exists in the game then store it in the array debuffList. Code example follows:

local debuffList = {}
 
SLASH_CMD1 = '/cmd'
function SlashCmdList.CMD(msg, editbox)
    local command, rest = msg:match("^(%S*)%s*(.-)$")
    if command == "add" then
        if GetSpellInfo(rest) then -- GetSpellInfo() returns nil (false) if the spell does not exist.
            table.insert(debuffList, rest)
        else
            print("Unknown spell")
        end
    end
end

This code works fine in most cases but when the debuff does not share the same name as the spell this code does not work. For example; there is a debuff called weakened armor but it is applied using the spell sunder armor. If I want to add the debuff weakened armor it tells me that weakened armor is an unknow spell. Is there any way to check if a debuff exists in the game instead of checking if the spell exists in the game?