Add more tests for easycsv_read_value

Signed-off-by: Pradana AUMARS <paumars@courrier.dev>

tests/check_easycsv.c

@@ -99,6 +99,12 @@ START_TEST(test_easycsv_read_value)
   str = easycsv_read_value(csv, 3, 4);
   ck_assert_str_eq(str, "");
   free(str);
+
+  str = easycsv_read_value(csv, 4, 1);
+  ck_assert_ptr_null(str);
+
+  str = easycsv_read_value(csv, 3, 5);
+  ck_assert_ptr_null(str);
   
   easycsv_free(csv);
 }