Update keymap.c

Co-Authored-By: Joel Challis <git@zvecr.com>

keyboards/maartenwut/ta65/keymaps/default/keymap.c

@@ -20,7 +20,7 @@ const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
 
 void encoder_update_user(uint8_t index, bool clockwise) {
   if (index == 0) { /* First encoder */
-    switch(biton32(layer_state)){
+    switch(get_highest_layer(layer_state)){
       case 0: //Layer 0
         if (!clockwise) { // Remove ! to reverse direction
           tap_code(KC_VOLU);
@@ -44,4 +44,4 @@ void encoder_update_user(uint8_t index, bool clockwise) {
         break;
     }
   }
-}
+}