Add nil guards and verbose warnings for MyVehicleConfig across client modules

[Copilot]

When external ulc.lua files contain syntax errors, server-side loading fails and MyVehicleConfig remains nil, causing cascading client-side errors when attempting to access its properties.

Changes

• Client-side nil guards: Added defensive checks before accessing MyVehicleConfig properties in all 9 client modules (buttons, stages, brake, horn, park, cruise, signals, doors, reverse)
• Contextual error messages: Added informative errors in helper functions that guide users to check server console for syntax error details
• Verbose warning messages: Added warning logs to internal functions and event handlers that alert when they're called inappropriately without a valid configuration, helping diagnose when functions shouldn't be executing
• Server-side diagnostics: Enhanced error output to explicitly label syntax errors with hints about common issues (missing commas, brackets, quotes)

Example

-- Before: crashes with "attempt to index a nil value"
function GetExtraByKey(key)
    for _, v in pairs(MyVehicleConfig.buttons) do
        if v.key == key then return v.extra end
    end
end

-- After: fails gracefully with actionable error
function GetExtraByKey(key)
    if not MyVehicleConfig then
        print("[ULC:GetExtraByKey] ERROR: MyVehicleConfig is not loaded. This usually means there's a syntax error in your ulc.lua file. Check server console for details.")
        return nil
    end
    for _, v in pairs(MyVehicleConfig.buttons) do
        if v.key == key then return v.extra end
    end
end

-- Internal functions also log warnings when called inappropriately
local function setBrakeExtras(newState)
    if not MyVehicleConfig then
        print("[ULC:setBrakeExtras] WARNING: Function called but MyVehicleConfig is not loaded. This function should not be called without a valid configuration.")
        return
    end
    -- function continues...
end

Script continues running when configs fail to load instead of producing repeated uncaught errors. Warning messages help identify when functions are being called in invalid states, making debugging easier.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Uncaught error</issue_title>
<issue_description>

Probably just a syntax error in ulc.lua but it would be nice to catch it when config isn't loaded

Would be even better if there was a way to actually call the ulc.lua so it can tell us the problem somehow</issue_description>

<agent_instructions>Can you come up with an elegant way to catch these errors and add context to them?
MyVehicleConfig is usually not available due to syntax errors or similar issues. </agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Uncaught error #37

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[Flohhhhh]

Looks good, but let's be slightly more verbose overall, for example i think we really should never be calling a lot of these things at all when MyVehicleConfig is nil

It would be nice to log some sort of warning in case we try to do something we shouldn't.

[Copilot]

Looks good, but let's be slightly more verbose overall, for example i think we really should never be calling a lot of these things at all when MyVehicleConfig is nil

It would be nice to log some sor...

Added verbose warning messages to all internal functions and event handlers that shouldn't be called when MyVehicleConfig is nil. Now functions like setBrakeExtras, setCruiseLights, onDoorStateChange, setReverseExtras, and others will log clear warnings if they're inappropriately called without a valid configuration. (commit 1f53b15)