Only consider multiplicitous entries.

src/serialization.rs

@@ -344,7 +344,7 @@ pub(super) fn find_most_common_histogram_entry_with_default<T: Copy>(histogram:
 }
 
 pub(super) fn find_leading_histogram_entries(histogram: HashMap<NodeFeatures, usize>, count: usize) -> Vec<NodeFeatures> {
-	let mut entry_counts: Vec<_> = histogram.iter().collect();
+	let mut entry_counts: Vec<_> = histogram.iter().filter(|&(_, &count)| count > 1).collect();
 	entry_counts.sort_by(|a, b| b.1.cmp(&a.1));
 	entry_counts.into_iter().take(count).map(|a| a.0.clone()).collect()
-}
+}