Cannot convert object to primitive value

In `almanac` you have debug lines like this:
```js
(0, _debug2.default)('almanac::constructor initialized runtime fact:' + fact.id + ' with ' + fact.value + '<' + _typeof(fact.value) + '>');
```
This line does string concatenation on `fact.value` which seems to also consider passed in `params` as facts. This basically requires that all passed in `params` have a `toString()` function such as what is available in a prototype. However, not all JavaScript variables are guaranteed to have a prototype or a `toString()` function (e.g. `new Object(null)`).

For starters, since this appears to be a debug log line, is there a way to disable this entirely? If not, this should be changed to use something like `fast-safe-stringify` or similar to convert param values to a String form.

该 issue 指出了 almanac 的一行调试日志；从这里开始，并使用 `new Object(null)` 复现该故障。当调试日志能够处理该值而不抛出异常，并且所选择的行为已由回归测试覆盖时，即表示完成。

由索引模型根据 Issue 内容生成。