only 1 value on map legend

[Ryan Batt]

For the neighborhood maps, if there is only 1 site with significant local autocorrelation, then the color bar only shows a single value, and this value does not match the color of the dot. E.g., SEUS Total Extinction:

It's probably because I do something like

r <- range(values)
bar_vals <- seq(r[1], r[2], length.out=3)

So when there is only one value, there is no from value in the call to seq. Could use an if() to make it ±0.01 around the single value, which should place the single value in the middle of the color bar, where it belongs. Might also check how R does its axes, e.g., via pretty().