Unsoundness/inconsistency with to_real

[11fb5c7](https://github.com/Z3Prover/z3/commit/11fb5c7dc49d879cdc2a3c3c4a732cd3c39749c5)
````
$ cvc5 -q --check-models bug.smt2
sat
$ z3 model_validate=true bug.smt2
unsat
$ cat bug.smt2
(declare-fun x () Real)
(assert (xor (is_int (to_real (* 2 x))) (<= 2 2)))
(check-sat)
````