Fixed an unused value.

tests/cmocka/DString_tests.c

@@ -231,7 +231,7 @@ void test_SCDString_split(void **state) {
 
     assert_true(SCDString_alloc(&dstr, " Hello World", strlen(" Hello World")) == SCUFCONT_SUCCESS);
     arr_len = 0;
-    res = SCDString_split(&dstr, " ", &arr, &arr_len);
+    assert_true(SCDString_split(&dstr, " ", &arr, &arr_len) == SCUFCONT_SUCCESS);
     assert_true(arr_len == 3);
     assert_string_equal(SCDString_c_str(arr), "");
     assert_string_equal(SCDString_c_str(arr + 1), "Hello");