fix: only typeset if MathJax is initialized

[weiseng18]

Problem

Refer to #60

Solution

Only attempt MathJax.typeset() if MathJax is defined

Checklist

• If the branch was not created off latest develop, merge locally
• Using latest develop and master, do git diff --stat master while in develop branch. Ensure that the diff is not too large
• If this is a feature, has appropriate documentation been added?

Notes

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