If:
(a) it is material in any proceedings for a court to be satisfied that an entry, search, seizure or other exercise of power was authorised in accordance with section 539; and
(b) a warrant signed by a magistrate under section 539 authorising the entry, search, seizure or other exercise of power is not produced in evidence;
the court is to assume, unless the contrary is proved, that the entry, search, seizure or other exercise of power was not authorised by such a warrant.