fix: correctly empty bitmap container iter when advancing past the back

Author: Dr-Emann

roaring/src/bitmap/store/bitmap_store.rs

@@ -515,6 +515,9 @@ impl<B: Borrow<[u64; BITMAP_LENGTH]>> BitmapIter<B> {
                 } else if cmp == Ordering::Equal {
                     self.value_back
                 } else {
+                    // New key is greater than original key and key_back, this iterator is now empty
+                    self.key = self.key_back;
+                    self.value = 0;
                     self.value_back = 0;
                     return;
                 }

roaring/tests/iter_advance_to.rs

@@ -255,3 +255,14 @@ fn advance_run_with_nth() {
     iter.advance_back_to(101779);
     assert_eq!(iter.nth(100563), None);
 }
+
+#[test]
+fn advance_bitset_front_and_back_past_each_other() {
+    let mut bitmap = RoaringBitmap::new();
+    bitmap.insert_range(0..=0x4000);
+    bitmap.remove_run_compression();
+    let mut iter = bitmap.iter();
+    iter.advance_back_to(100);
+    iter.advance_to(300);
+    assert_eq!(iter.next(), None);
+}