Fix test

Author: morenol

src/svm/svc.rs

@@ -719,6 +719,9 @@ impl<'a, T: RealNumber, M: Matrix<T>, K: Kernel<T, M::RowVector>> Optimizer<'a,
         idx_2: Option<usize>,
         cache: &mut Cache<'_, T, M, K>,
     ) -> Option<(usize, usize, T)> {
+        if self.sv.is_empty() {
+            return None;
+        }
         match (idx_1, idx_2) {
             (None, None) => {
                 if self.gmax > -self.gmin {