Fixed invalid variable usage added cargonet logic check

[Sycholic]

Fixed the 2 invalid calls to _vehicle local variable that doesnt exist anymore in the script.
Created a logic check to see if the vehicle even has a cargo net in the first place then check logic for the cargo net being visible.

Short circuit logic (Lazy Evaluation as arma calls it) is used here 2nd part of logic is not even evaluated if the cargo net does not exist for the target.

[Sycholic]

btw I wrote that with the camonet checking to make sure it exists first. server side log is getting spammed with tons upon tons of bad animation/texture missing/dont exist errors. so figured for sanity sake since that script is rarely called.