fixes #9241: enable collapsing for labels, in addition to badges, when empty

less/badges.less

@@ -18,7 +18,7 @@
   background-color: @badge-bg;
   border-radius: @badge-border-radius;
 
-  // Empty labels/badges collapse
+  // Empty badges collapse automatically (not available in IE8)
   &:empty {
     display: none;
   }

less/labels.less

@@ -23,6 +23,11 @@
       cursor: pointer;
     }
   }
+
+  // Empty labels collapse automatically (not available in IE8)
+  &:empty {
+    display: none;
+  }
 }
 
 // Colors