The OP asked about the WPA rule and in the situation he described, if no balls went down, the incoming shooter must take the balls in position.
As far as I know, the WPA hasn't amended the rules to include an alternative set where you can give the table back on any miss.
Some events, like the Tony Robles/Predator events, play option on any miss. Hopkins SBE has played it both ways in recent years, I believe most recently with the option on any miss as a concession to the players "union" that prefers it that way. But this is not in the WPA rule set.
The interesting thing is that in response to the question posed in the thread title, you do not ever have to call a safety under WPA rules. The reason being that even if you call a safety, if a ball goes down the incoming player has the option. You cannot call a safety, pocket a ball, and force your opponent to take the table in position. The treatment is exactly the same as missing a shot - if a ball falls incoming player has the option; if no ball falls incoming player takes table as is. Thus no need to call a safety under WPA rules.
Essentially the two rule sets come down to whether you want to do away with the two-way shot in order to do away with the occasional accidental (oopsy, sorry about that) snooker.