It's not really appropriate to use the term "force" unless it is associated with a massive object, as in $F = ma$, or with something like spring compression or string tension.
In the situation you've described, the magnetic field at the "null" point is not acting on anything. If you were to measure the field strength at that point, e.g., by observing a moving charged particle there or by placing a magnetic dipole there, you would of course determine that the field strength there is zero.
The magnetic force acting on each point of either of the two bar magnets in your example depends only on the magnetic field's strength and divergence at that point of the bar magnet; it does not depend directly on the field strength or divergence anywhere else. So, it is not really meaningful to refer to attraction or repulsion at a point outside the bar magnets. Similarly, if there were a cavity inside one of the bar magnets there would be a magnetic field in the cavity, but there would be no repulsion or attraction occurring within the cavity.
There could be some misunderstanding of what's going on at that "null field" point. It kind of looks as if the field lines are repelling each other there, but that's not really what's happening. At every point in the field, the net field strength and direction is simply the vector sum of the field strength and direction of all the sources in the surrounding space. When that vector sum is mapped out, the map looks like field "lines", but the lines are not objects or even a substance like gas. They are more like lines drawn perpendicular to the contour lines in a topographic map.