Fix mermaid.js can't use with prism.js

[Nyx1197]

Hi~ I fix some error when use mermaid.js with prism.js. You can verify by create article and write example code.

你好~ 我修复了 mermaid.js 无法与 prism.js 一起使用的问题, 包括一个js报错以及图表无法正常渲染. 你可以通过创建一个文章并输入示例代码来测试

example code is here, don't forgot delete / 示例代码如下, 测试的时候需要删除掉 /

title

/```mermaid flowchart LR A[Hard] -->|Text| B(Round) B --> C{Decision} C -->|One| D[Result 1] C -->|Two| E[Result 2]

/```

JavaScript Code Test

/```js var a = 1; var b = 2; return a + b;

/```

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