How to initialize an array in PL/SQL?

If I create a RECORD TYPE, then create a TABLE TYPE based on the RECORD TYPE, I have not problem to put the data in. But I have problem to re-initalize the TABLE TYPE.

DECLARE    TYPE t_abc_record IS RECORD

     (field_1   NUMBER,
      filed 2   NUMBER);

   TYPE t_table IS TABLE OF t_abc%ROWTYPE    INDEX BY BINARY_INTEGER;    v_abc_rec t_abc_record;
   v_abc_table t_table;

BEGIN    v_abc_table.field_1 := 1;
   v_abc_table.field_2 := 2;

   v_abc_table := NULL; (program crash)

END;

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Best regards,