in cover_tree.rs i64::MIN - 1 causes overflow. FIXED. (#361)

* in cover_tree.rs i64::MIN - 1 causes overflow. FIXED.

Author: skywardfire1

src/algorithm/neighbour/cover_tree.rs

@@ -290,7 +290,10 @@ impl<T: Debug + PartialEq, D: Distance<T>> CoverTree<T, D> {
             self.new_leaf(p)
         } else {
             let max_dist = self.max(point_set);
-            let next_scale = (max_scale - 1).min(self.get_scale(max_dist));
+            let next_scale = max_scale // bugfix i64::MIN - 1 causes overflow
+                .checked_sub(1) // returns None if overflow
+                .map(|s| s.min(self.get_scale(max_dist)))
+                .unwrap_or(i64::MIN); // safely getting required value
             if next_scale == i64::MIN {
                 let mut children: Vec<Node> = Vec::new();
                 let mut leaf = self.new_leaf(p);

src/metrics/distance/jaccard.rs

@@ -89,7 +89,6 @@ mod tests {
         all(target_arch = "wasm32", not(target_os = "wasi")),
         wasm_bindgen_test::wasm_bindgen_test
     )]
-
     #[test]
     fn jaccard_distance() {
         let a = vec![1, 0, 1, 1];
@@ -133,4 +132,3 @@ mod tests {
         assert!((d1 - d2).abs() < 1e-12);
     }
 }
-