fix(toolbox): Background of disabled settings button & tileview button

css/_settings-button.scss

         }
 
         &.settings-button-small-icon--disabled {
+            background: #36383C;
+
             &> svg {
                fill: #929292;
            }

react/features/toolbox/components/web/Toolbox.js

                 ? mainMenuAdditionalButtons.push(
                     <TileViewButton
                         key = 'tileview'
-                        showLabel = { false }
-                        visible = { true } />)
+                        showLabel = { false } />)
                 : overflowMenuAdditionalButtons.push(
                     <TileViewButton
                         key = 'tileview'