Whenever a new city has been or shall be incorporated but such incorporation shall not have been completed by the adoption of a city charter, then any notice required by this chapter to be served upon the city clerk shall be served upon the clerk or clerks of the township or townships from which the city was incorporated: Provided, That if a city charter shall have been submitted, but rejected by the electors, then such notice shall also be served upon the de facto officer of the city, if there be such an officer. Service of any notice made prior to the effective date of this amendment, which was made in the manner provided in this section, is hereby declared to be a valid compliance with the terms of this act in respect to service upon the city clerk.