Issue #3540091: Add check if proximity is NaN

Closes #3540091 This is to avoid returning NaN when deriving the proximity of 2 places that have almost the same location/coordinates, and setting the proximity to 0 instead in this instance. Someone with a good grasp of the math that calculates proximity might better understand when NaN will result. I only know it did for Normal, AL and Alabama A&M University, and then noticed they have almost the same coordinates.