verify_point() does not catch missing point estimates without rows

[nickreich]

The function is only designed to capture situations in which the point estimate is NA, but if a row repreesnting a point estimate for a particular target-location is entirely missing (i.e. the row just isn't in the file at all), the entry still passes this verification. It should be set up so that the function also looks to make sure point estimates for each target-location pair are present.