Maybe this is defined as something that has not yet come into the world.

??
This is a completely ordinary conditional oath. It has nothing to do with the topic of something that has not yet come into the world.

Suppose I swear to sell you fruit from a tree when the fruit does not yet exist. When the fruit comes into being, am I obligated to sell it to you?
I understand that there may be a distinction between this and an example like: if Ukraine defeats Russia, I will sell you fruit. But I only gave an illustration in which the oath could be connected to something that has not yet come into the world.

When you swear to sell something that has not yet come into the world, that is an oath in every respect. You cannot transfer ownership of something that has not yet come into the world, but an oath is always about a future act. When you swear to sell something, you are swearing about an act, not transferring ownership. There is no problem at all with doing that regarding something that has not yet come into the world.
But all this is not relevant to our question, because here we are not talking about transferring ownership of something future, but about an oath on a condition. A conditional oath is always making a future act depend on a future state of affairs. There is nothing special here, and it is an ordinary oath that of course is binding.

Sorry, I meant to write in the question that the condition was not fulfilled.
Apparently that got left out.
X did not happen. And the question is whether there is any value in carrying out the oath.

If the condition was not fulfilled, the oath does not take effect. However, that is only if you formulated the condition according to the laws of conditions: a doubled condition, the positive before the negative, and the condition before the act, and provided that you did not make a condition against what is written in the Torah and that it is something possible to fulfill. If you formulated it differently, then it is possible that the oath takes effect anyway.

So I'll send an email to ask.

I was wondering whether there is a difference between an oath, which applies to the person, and a vow, which applies to the object, with respect to something that has not yet come into the world. For example: if a person vows not to eat the fruit that will come from the tree when it does not currently exist, since a vow applies to the "object" and the fruit does not exist, this is exactly like selling that fruit. Isn't that so?

Correct. But there is no problem with an oath on the person that he will sell fruit.