title: R ggplot geom_text wipes out background--bug?
body: <p>I found an issue with ggplot2::geom_text() when I attempt to highlight my data with labels. My MWE illustrates the situation. After I define the plot I add the theme() from phase#1 which colors the panel and plot backgrounds. The red/green is for emphasis. When the labels are added in phase#2, the plot.background goes to white and the panel background to the default grey. Is this something I'm doing, is this an undocumented feature of ggplot2, or is this a bug?</p>
  
  <pre><code> require(ggplot2)
  
   SESnow &lt;- data.frame(Year=c(1978,1988,1995,2000,2013,2017), 
                   Snow=c(355.9,322.1,329.1,303.6,318.5,304.0))
  
  p &lt;- ggplot(SESnow, aes(x=Year, y=Snow, fill=Snow)) +
  geom_col(width=1)  + 
  scale_fill_gradient(low="blue", high="red",  limits=c(0,400)) +
  theme(axis.title.y=element_text(angle=0)) +
  ggtitle("Yearly Total Snowfall (inch)") + 
  labs(subtitle = "Copper City 2019", 
     caption="Source: Keweenaw County", 
     x="Snow Season") +
  theme(legend.position="none")
  
  #phase#1
  p + theme( panel.background = element_rect(fill = "green",
                                         colour = "black",
                                         size = 0.5, linetype = "solid"),
         plot.background = element_rect(fill = "blue",
                                        colour = "black",
                                        size = 0.5, linetype = "solid"),
         axis.text.x = element_text(colour="grey20",size=11, vjust=1,
                                     margin=margin(t=0,b=0),face="bold"),
         axis.text.y = element_text(colour="grey20",size=11,  hjust=1,
                                     margin=margin(t=10,b=10),face="bold") )
  
  #phase#2
  p + geom_text(data=SESnow, aes(label = Snow, fill=NULL ),  y = SESnow$Snow + 20.0, 
          label=format(SESnow$Snow, digits=2), size=3, fontface="bold",
          color="black")
  </code></pre>
  
  <p>Also note that if you run phase#1 after phase#2 the labels disappear, so this feature is consistent. How do I get a plot with labels and colored background?</p>