No check for empty array in trigger

In following picture, v_Department_list is an array (filled automatically by multiple select widget displayed as menu), in the trigger I must check if this array is NOT empty to make a logic flow with it, otherwise, show a message, of course I can first check if it is empty, show the message and than do whatever I need to do, but why ? why insn’t there an option to check if the array is not empty by first place ?


Thank you,
Amit Berku