Below is the error I was getting. I saved and copied / pasted its string because the function is working after I have changed the condition to test "unitID".
String with the error:
Lua Code:
1x HiddenFrames\core.lua:70: Usage: UnitInVehicle("unit")
[C]: in function `UnitInVehicle'
HiddenFrames\core.lua:70: in function `?'
...ibraries\CallbackHandler-1.0\CallbackHandler-1.0-7.lua:119: in function <...ibraries\CallbackHandler-1.0\CallbackHandler-1.0.lua:119>
[C]: ?
...ibraries\CallbackHandler-1.0\CallbackHandler-1.0-7.lua:29: in function <...ibraries\CallbackHandler-1.0\CallbackHandler-1.0.lua:25>
...ibraries\CallbackHandler-1.0\CallbackHandler-1.0-7.lua:64: in function `Fire'
ElvUI\Libraries\AceEvent-3.0\AceEvent-3.0-4.lua:120: in function <ElvUI\Libraries\AceEvent-3.0\AceEvent-3.0.lua:119>