ggplot2报错Error in grid.Call(L_textBounds, as.graphicsAnnot(x$label), x$x, x$y, : 找不到多边形的边

ggplot(airquality,aes(Wind,Temp)) + geom_point(color='steelblue',alpha=0.4,size=5)

运行后报错：

Error in grid.Call(L_textBounds, as.graphicsAnnot(x$label), x$x, x$y,  : 

  找不到多边形的边