In any case in which two or more defendants are jointly charged in the same complaint, indictment, or information, and the court or magistrate, for good cause shown, continues the arraignment, preliminary hearing, or trial of one or more defendants, the continuance shall, upon motion of the prosecuting attorney, constitute good cause to continue the remaining defendants’ cases so as to maintain joinder. The court or magistrate shall not cause jointly charged cases to be severed due to the unavailability or unpreparedness of one or more defendants unless it appears to the court or magistrate that it will be impossible for all defendants to be available and prepared within a reasonable period of time.