test: uncaught exception when editing properties of a removed message

These two functions don't fail gracefully when editing a removed
message:
 BROKEN edit property on removed message without uncaught exception
        --- T610-message-property.20.EXPECTED   2023-02-27 11:33:25.792764376 +0000
        +++ T610-message-property.20.OUTPUT     2023-02-27 11:33:25.793764381 +0000
        @@ -1,2 +1,3 @@
         == stdout ==
         == stderr ==
        +terminate called after throwing an instance of 'Xapian::DocNotFoundError'

The other functions appear to be safe.