[Addon Parsing Bug]XML errors might appear after a addon is disabeled

zgrssd

This is part bug report (to complex to ingame function), part information for fellow programmers.

Affected Version:
EU client
The Client state at 26th May 2014, 7 PM (UTC)

While testing some code today I ran into an odd issue:
I had an XML file to incerept the Update event. But my lua file with the event code was faulty, so the addon failed while parsing the lua file (I forgot to write function before the function name).
Naturally a fail there would also mean that the events parameter is still nil when it comes to parsing the .xml file, but since .lua is parsed before .xml the .xml should never have run.

Then I tried to disable it in a bet to check if if was really this addon (even though it was the only one I had running at that time).
And on the first UI reload after the addon was disabeled the game threw me the .xml parsing error ("nil where value expected"). On the next reload nothing happened.

So "if a lua error would result in the XML running into a nil argument exception, that exception message will appear in the reload after the Addon has already been disabeled."

Code to reproduce:

## Title: LibHeadingChange
## APIVersion: 100004

HeadingChange.lua
HeadingChange.xml

local onUIUpdate() -- faulty, 'function' is missing causing parsing error.
end

--Explicit exposure of local function globally
LibHeadingChange = { onUIUpdate = onUIUpdate }

return LibHeadingChange

<GuiXml>
    <Controls>
        <TopLevelControl name="UI_UpdateInterceptor" movable="false">
            <Dimensions x="58" y="58" />
            <Anchor point="CENTER" />
            
            <OnUpdate>
                LibHeadingChange.onUIUpdate()
            </OnUpdate>
        </TopLevelControl>
    </Controls>
</GuiXml>