Update changelog.d/6747.bugfix

Co-Authored-By: Erik Johnston <erik@matrix.org>

changelog.d/6747.bugfix

-Fix infinite recursion and dictionary access bug when setting `account_validity` to an empty block in the homeserver config. Thanks to @Sorunome for reporting.
+Fix bug when setting `account_validity` to an empty block in the config. Thanks to @Sorunome for reporting.
\ No newline at end of file