treat stroke == NA as 0 (#4667)

Author: thomasp85

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 (development version)
 
+* Setting `stroke` to `NA` in `geom_point()` will no longer impair the sizing of
+  the points (@thomasp85, #4624)
+
 * `stat_bin_2d()` now correctly recognises the `weight` aesthetic 
   (@thomasp85, #4646)
 

R/geom-point.r

@@ -122,6 +122,8 @@ GeomPoint <- ggproto("GeomPoint", Geom,
     }
 
     coords <- coord$transform(data, panel_params)
+    stroke_size <- coords$stroke
+    stroke_size[is.na(stroke_size)] <- 0
     ggname("geom_point",
       pointsGrob(
         coords$x, coords$y,
@@ -130,7 +132,7 @@ GeomPoint <- ggproto("GeomPoint", Geom,
           col = alpha(coords$colour, coords$alpha),
           fill = alpha(coords$fill, coords$alpha),
           # Stroke is added around the outside of the point
-          fontsize = coords$size * .pt + coords$stroke * .stroke / 2,
+          fontsize = coords$size * .pt + stroke_size * .stroke / 2,
           lwd = coords$stroke * .stroke / 2
         )
       )