message: fix(css): add white bg to masthead header
diff: @@ -23,6 +23,7 @@ $search-transition-timing: 95ms;
  transition-delay: 200ms;
  transition-timing-function: $search-transition;
  transition-duration: 300ms;
  + background-color: $ui-background;
  &--sticky {
  &.#{$prefix}--masthead--sticky__l1 {
  