Fix double icon on header button hover

app/assets/stylesheets/themes/ui_mars.scss

@@ -37,9 +37,6 @@
           background-image: -o-linear-gradient(#595D63 6.6%, #202227);
           background-position:0 0;
           color:#fff;
-          i { 
-            @extend .icon-white;
-          }
         }
 
         border: 1px solid #31363E;

app/assets/stylesheets/themes/ui_modern.scss

@@ -70,9 +70,6 @@
         color:#ccc;
         &:hover {
           color:#fff;
-          i { 
-            @extend .icon-white;
-          }
         }
         border: none;
         box-shadow:none;