gg: fix native image rendering with with/height=0

vlib/gg/image.c.v

@@ -283,8 +283,18 @@ pub fn (ctx &Context) draw_image_with_config(config DrawImageConfig) {
 				}
 				x := config.img_rect.x
 				y := config.img_rect.y
-				C.darwin_draw_image(x, ctx.height - (y + config.img_rect.height), config.img_rect.width,
-					config.img_rect.height, img)
+				width := if config.img_rect.width == 0 {
+					f32(img.width)
+				} else {
+					config.img_rect.width
+				}
+				height := if config.img_rect.height == 0 {
+					f32(img.height)
+				} else {
+					config.img_rect.height
+				}
+				C.darwin_draw_image(x, ctx.height - (y + config.img_rect.height), width,
+					height, img)
 				return
 			}
 		}