This Taproot transaction has 3 witness gadgets that are preliminary stack for P2TR script. Execution of the tapscript goes one thing like this:

1. push (4 gadgets on the stack)
2. checksig operation (leads to pushing 1 on the stack – we’re again on a 3 gadgets on the stack)
3. push an empty aspect (4 gadgets on the stack)
4. OP_IF with an empty aspect as an enter; it doesn’t consider (3 gadgets on the stack)
5. the tip (3 gadgets on the stack)

Because the consensus rule for tapscript is that execution cannot lead to something however precisely one aspect on the stack which evaluates to true, I’m asking how is that this transaction legitimate?