Yes, That script is not good, Use this one:
elseif ($2 == !burn) {
if ($vcmp.cmdcheck(!burn,%id) == fail) !halt
elseif (!$3) vcmp.msg %id Error - Missing Information, $2 <car id>
elseif ($3 !isnum) vcmp.msg %id Error - Invalid Vehicle ID, $2 <car id>
else {
vcmp.setvehiclehp $3 0
vcmp.msg %id Your car is burning..
}
}