If the redevelopment agency has, prior to merger of redevelopment project areas pursuant to Section 33470, incurred any indebtedness on account of a constituent project area so merged, taxes attributable to such area which are allocated to the agency pursuant to subdivision (b) of Section 33670 shall be first used to comply with the terms of any bond resolution or other agreement pledging such taxes from such constituent project area until a refunding has occurred which satisfies the terms of such resolution or agreement.