Attempt to call global a nil value?

[AeroMaxxD]

Would anyone happen to know why self would be a nil value?

This has been working perfectly fine for a few days, but I must have broken it somehow, I stripped the code right back to try and hung down what I broke, but I still get the error.

1x [string "*OnloadTest.xml:25_OnLoad"]:1: attempt to call global 'AMD_OnLoad' (a nil value)
[string "*OnloadTest.xml:25_OnLoad"]:1: in function <[string "*OnloadTest.xml:25_OnLoad"]:1>

Locals:
self = AMD_TabOnCharacterFrame {
 0 = <userdata>
}
(*temporary) = nil
(*temporary) = AMD_TabOnCharacterFrame {
 0 = <userdata>
}
(*temporary) = "attempt to call global 'DGT_OnLoad' (a nil value)"

local TabName="AMD";
local TabID=CharacterFrame.numTabs+1;
local Tab=CreateFrame("Button", "$parentTab"..TabID, CharacterFrame, "CharacterFrameTabTemplate", TabID);
PanelTemplates_SetNumTabs(CharacterFrame, TabID);
Tab:SetPoint("LEFT", "$parentTab"..(TabID-1), "RIGHT", -16, 0);
Tab:SetText(TabName);
-- Tab:SetID(TabID);
 
tinsert(CHARACTERFRAME_SUBFRAMES, "AMD_TabOnCharacterFrame");
 
hooksecurefunc("CharacterFrameTab_OnClick", function(self, button)
    if self:GetID() == TabID then
        ToggleCharacter("AMD_TabOnCharacterFrame")
    end
end)
 
function AMD_OnLoad(self)
    print("AddOn loaded")
end

<Ui xmlns="http://www.blizzard.com/wow/ui/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.blizzard.com/wow/ui/ http://wowprogramming.com/FrameXML/UI.xsd">
	<Frame name="AMD_TabOnCharacterFrame" parent="CharacterFrame" frameStrata="HIGH" enableMouse="true" movable="true" setallpoints="true" id="4">
		<Size x="206" y="580"/>
		<Frames>
			<Frame name="$parent_History" parent="AMD_TabOnCharacterFrame">
				<Size x="300" y="325"/>
				<Anchors>
					<Anchor point="CENTER" relativePoint="CENTER" relativeTo="CharacterFrame"/>
				</Anchors>
				<Layers>
					<Layer level="OVERLAY">
						<FontString name="History_Title" parentKey="History_title" inherits="GameFontNormal">
							<Color r="1" g="1" b="1" a="1"/>
							<Anchors>
								<Anchor point="TOP">
									<Offset x="0" y="20"/>
								</Anchor>
							</Anchors>
						</FontString>
					</Layer>
				</Layers>
			</Frame>
		</Frames>
		<Scripts>
			<OnLoad>
				AMD_OnLoad(self)
			</OnLoad>
		</Scripts>
	</Frame>
</Ui>