allow len without is_empty

src/taiko/mod.rs

@@ -170,6 +170,7 @@ pub struct TaikoStrains {
 impl TaikoStrains {
     /// Returns the number of strain peaks per skill.
     #[inline]
+    #[allow(clippy::len_without_is_empty)]
     pub fn len(&self) -> usize {
         self.color.len()
     }