In the Bavli, Shabas 7, amud 1, Rashi twice uses the word "בטל" in contexts where I don't understand its meaning. I wonder whether anyone can help.
The first time is:
ברשות הרבים כי האי גוונא מקום פטור הוא ובטל ומותר לרשות הרבים ולרשות היחיד
In a public thoroughfare, such a thing [viz, something less than four tefach wide] is a m'kom p'tur (place of exemption), and it is בטל and permitted to the public thoroughfare and to the private property.
The second is the hypothesis
דאין רה״י שולטת בחצר באויר למעלה מי׳ אלא מקום פטור הוא ובטל אף לגבי רה״ר
that private property doesn't control, in a yard, the air above ten tefach: rather, it's a m'kom p'tur and בטל even vis à vis the public thoroughfare.
What is this בטל? What sort of being nullified or canceled (I guess, since those are its usual meanings) is this? What does בטל mean here?