CombinationsWithReplacement::nth: slightly faster fix

src/combinations_with_replacement.rs

@@ -107,16 +107,17 @@ where
     }
 
     fn nth(&mut self, n: usize) -> Option<Self::Item> {
-        if self.first {
+        let times = if self.first {
             // In empty edge cases, stop iterating immediately
             if !(self.indices.is_empty() || self.pool.get_next()) {
                 return None;
             }
             self.first = false;
-        } else if self.increment_indices() {
-            return None;
-        }
-        for _ in 0..n {
+            n
+        } else {
+            n + 1
+        };
+        for _ in 0..times {
             if self.increment_indices() {
                 return None;
             }