Then what does this belief not allow to happen—what would definitely falsify this belief? A null answer means that your belief does not constrain experience; it permits anything to happen to you.

What if I had the belief that a certain coin was unfair, with a 51% chance of heads and only 49% chance of tails? Certainly I could observe an absurd amount of coin flips, and each bunch of them could nudge my belief -- but short of an infinite number of flips, none would "definitely" falsify it. Certainly in this case, I could come to believe with an arbitrary level of certainty in the falsehood of the belief. But I don't believe that would apply in general -- what if to reach any arbitrary level of testing a belief, I'd need to think up and apply an indefinite number of unique tests? For example, a belief concerning the state of mind of another person -- I can't think of a definite test, nor can I repeat any test indefinitely to increase certainty.

On a related note, why abandon Bayes in this case for Popper, without any disclaimer? Eg falsificationism is useful because it fights magic explanations and positive bias, but it is still a predictive belief if observation causes you to slightly shift your probability for that belief.