title: Error in FUN(X[[i]], ...) : object not found when adding geom_text with facet
body: <p>Adding   geom_text(data = dat_text, mapping = aes(x , y , label = label)) 
   line gives me the following error: Error in FUN(X[[i]], ...) : object 'sex' not found. This is so irrelevant that I have no idea what to do with it. </p>
  
  <p>Without the last line, the ggplot generates the graph just fine. </p>
  
  <pre><code>dat_text &lt;- data.frame(
    label = c("Most unisex year", "Marion Jones wins gold in Olympic", "Jackie Robinson to major leauge", "Jamie Hunter Cartwright appears on Bonanza", "The Little Mermaid sways Ariel towards girls"),
    cyl   = c("Jessie", "Marion", "Jackie", "Jamie", "Ariel"),
    x     = c(1940, 1940, 1940,1940, 1940),
    y     = c(.3, .4, .2,.2,.3))
  
  # make the plot here
  data.babyname.all %&gt;% 
    ggplot( mapping = aes(x = year, y = perc, fill = sex)) +
    geom_density(stat = "identity", position = "stack" , show.legend = F ) +
    scale_fill_manual(values = c('#E1AEA1','#9ABACF'))  + 
    geom_point(data = most.unisex.year.and.value, mapping = aes(x =  year, y = perc), 
               size = 3, 
               fill = "white", 
               color = "black", 
               shape = 21) +
    facet_wrap(~name, ncol= 7, nrow=5) +
    theme_minimal() + #set theme
    theme(panel.grid.major = element_blank(),
          panel.grid.minor = element_blank(),
          panel.background = element_blank(),
          panel.border = element_blank(),
          text = element_text(size = 12),
          panel.grid = element_blank(),
          axis.title.x= element_blank(),
          axis.title.y=element_blank(),
          plot.background = element_blank(),
          axis.ticks.x = element_line(color = "black"),
          axis.ticks.length = unit(0.1, "cm")) + 
    scale_y_continuous(breaks = c(0,.50,1), labels= c("0%", "50%","%100")) +
    scale_x_continuous(breaks = c(1940, 1960, 1980,2000), labels= c('1940', "'60","'80",'2000')) +
    geom_text(data = dat_text, mapping = aes(x , y , label = label)) 
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/7dLpf.png" rel="nofollow noreferrer">image of what I get without the last line</a></p>