You can prevent the request being send to server by throwing an error in pre-request script:
pm.request.url.toJSON().variable.filter((elem) => elem.value === "").map(elem => elem.key).includes("v2") ? (() => {throw Error("Please provide path parameter v2")})(): null
This code will check if the path parameter v2 (eg https://something/:v2/something) has a value provided else throw the error
