scrolling: Don't forget to call tab_indicator.update_shaders()

This didn't actually break anything since those shaders aren't
configurable.

src/layout/scrolling.rs

@@ -336,8 +336,8 @@ impl<W: LayoutElement> ScrollingSpace<W> {
     }
 
     pub fn update_shaders(&mut self) {
-        for tile in self.tiles_mut() {
+        for col in &mut self.columns {
-            tile.update_shaders();
+            col.update_shaders();
         }
     }
 
@@ -4056,6 +4056,14 @@ impl<W: LayoutElement> Column<W> {
         }
     }
 
+    pub fn update_shaders(&mut self) {
+        for tile in &mut self.tiles {
+            tile.update_shaders();
+        }
+
+        self.tab_indicator.update_shaders();
+    }
+
     pub fn advance_animations(&mut self) {
         if let Some(move_) = &mut self.move_animation {
             if move_.anim.is_done() {