So you have a topic you can argue about where the outcome of the argument doesn't really have any major effect on your life? That's great!
Some people approach a relationship with an attitude that any form of conflict must be avoided so you can be a constantly happy lovey-dovey couple. That's a mistake! One of the most important things for maintaining a long-term relationship is having a compatible conflict resolution strategy. In the long term, conflicts about important life decisions can not be avoided (I am not talking about "what movie do we watch tonight", more like "do we move to this or that city" or "are we ready to have children").
When such a conflict arrives, you and your significant other must have learned how to have a civilized and respectful discussion with each other. You also must have realized that a disagreement is not the end and that your relationship can recover from it. When you haven't done that before the big conflict arrives, your relationship is in serious danger of breaking up.
How to resolve conflicts with another person is something you have to practice with each person. So don't be afraid of irrelevant arguments, because it helps you to practice how to have an argument with that person without either of you getting hurt.
So if you come to a disagreement about whether or not white walkers are zombies, if the USS Enterprise would win against an imperial star destroyer or how lame it is that every high fantasy author just plagiarizes J.R.R. Tolkien (and we all know that there is exactly one right answer to each of these questions), delve right into it. See how far you can take it, be mad at each other, make up and laugh together about how ridiculous it was to get into a fight about something so trivial.
Or maybe you actually do end up breaking up about something that ridiculous. If you do, your relationship wasn't going to last anyway. It might not seem like that now, but in a few months you will realize it was for the better.