BugReport : ClassicAPI v1.15.15: invalid unit arguments reach UNIT_AURA addon handlers

[mrkoalaz]

I wrote this issue by codex, maybe it has some mistake

Body

### Summary

On Turtle WoW, buying items from a merchant with ClassicAPI v1.15.15 produces Lua usage errors in legacy addon libraries that handle unit aura events.

With pfUI v9.0.27 and the same addon setup, replacing only `ClassicAPI.dll` with v1.15.14 and repeating the merchant test produces no errors. Replacing it with v1.15.15 reproduces the errors.

This suggests a regression or interaction specific to v1.15.15, although I have not identified the exact event source.

### Environment

- Client: Turtle WoW (WoW 1.12 based)
- pfUI: v9.0.27
- ClassicAPI: v1.15.15 (errors reproduce); v1.15.14 (no errors in the same test)
- Trigger: buying multiple items from a merchant

### Errors

`HealComm-1.0.lua:1517`:

```text
Interface\AddOns\!Libs\HealComm-1.0\HealComm-1.0.lua:1517: Usage: UnitName("unit")
Count: 1

[C]: ?
[C]: in function `UnitName'
Interface\AddOns\!Libs\HealComm-1.0\HealComm-1.0.lua:1517: in function `obj_method'
...face\AddOns\!Libs\Ace2\AceEvent-2.0\AceEvent-2.0.lua:315: in function `TriggerEvent'
...face\AddOns\!Libs\Ace2\AceEvent-2.0\AceEvent-2.0.lua:902: in function <...face\AddOns\!Libs\Ace2\AceEvent-2.0\AceEvent-2.0.lua:894>

SpecialEvents-Aura-2.0.lua:250:

...SE\SpecialEvents-Aura-2.0\SpecialEvents-Aura-2.0.lua:250: Usage: UnitBuff("unit", index [,raidFilter])
Count: 2

[C]: ?
[C]: in function `UnitBuff'
...SE\SpecialEvents-Aura-2.0\SpecialEvents-Aura-2.0.lua:250: in function `obj_method'
...face\AddOns\!Libs\Ace2\AceEvent-2.0\AceEvent-2.0.lua:315: in function `TriggerEvent'
...face\AddOns\!Libs\Ace2\AceEvent-2.0\AceEvent-2.0.lua:902: in function <...face\AddOns\!Libs\Ace2\AceEvent-2.0\AceEvent-2.0.lua:894>

Both handlers appear to be receiving a missing or invalid unit argument through AceEvent.

Additional clue

An earlier occurrence of the UnitName error had these frames below the AceEvent dispatch:

[C] in function `RemoveNewItem'
Interface\AddOns\pfUI\modules\newitem.lua:31

The latest stack traces above do not include RemoveNewItem, so I cannot confirm whether that is the same trigger path.

I don't know what happend , the only situation i can confirm is use ClassicAPI 1.15.15 , I bought or pick new items will report two lua error above.