Twenty Eleven: Correct height for a Button block without text.

Props ianbelanger, laurelfulford, nayana123.
See #47414.

git-svn-id: https://develop.svn.wordpress.org/trunk@45763 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-content/themes/twentyeleven/editor-blocks.css

@@ -382,6 +382,10 @@ p.has-drop-cap:not(:focus)::first-letter {
 	text-shadow: 0 -1px 0 rgba(0,0,0,0.3);
 }
 
+.wp-block-button .wp-block-button__link[data-is-placeholder-visible=true] {
+    height: auto;
+}
+
 .wp-block-button__link {
 	background: #222;
 	color: #eee;