Question about using Assign Statement with Table Expression

Just a quick question for all the ABAP Experts out there.
For the below code should I use SY-SUBRC = 0 for the ASSIGN Keyword or CATCH CX_SY_ITAB_LINE_NOT_FOUND for the Table Expression? Not sure how this works... Thanks for any insight!

" CHECK IF EMPLOYEE FOUND IN BPC MASTER DATA DIM TABLE 
ASSIGN <lt_employee>[ (lc_id) = <lv_employee> ] TO FIELD-SYMBOL(<ls_employee>).