title: Can't get rid of padding at top of guide without a title
body: <p>I'm trying to generate a figure with the guide set into the plotting window. The guide should have a white background and a black borer. I'm mostly successful with this example code...</p>
  
  <pre><code>library(ggplot2)
  
  my_data &lt;- data.frame(treatment=rep(c("Treatment A","Treatment B"),50), x=runif(100), y=runif(100))
  
  ggplot(my_data, aes(x, y, color=treatment, shape=treatment)) +
      geom_point() +
      scale_color_manual(values=c('red', 'blue'), name=NULL) +
      scale_shape_manual(values=c(19,1), name=NULL) + 
      theme(
          legend.background = element_rect(color="black"),
          legend.position=c(0.65, 0.7),
          legend.title = element_blank()
      )
  </code></pre>
  
  <p>It generates a figure that looks like this:
  <a href="https://i.stack.imgur.com/TWIRB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TWIRB.png" alt="enter image description here"></a></p>
  
  <p>The problem is that there is extra padding above the line for Treatment A relative to the amount of padding along the bottom of the guid box. I've tried things like <code>legend.title = element_blank()</code>, <code>legend.title = element_text()</code>, and <code>legend.title = NULL</code>, but none of them improve the appearance. Any ideas?</p>