fix error when term1label is not a string

[congyu-lu]

Description

Checklist

Check each task that has been performed or verified to be not applicable.

• Tests: added and/or passed unit and integration tests, or N/A
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• Notable Changes: updated release.txt, prefixed a commit message with "fix:" or "feat:", added to an internal tracking document, or N/A

[xzhou82]

thanks but not the fix i want. this chart makes no sense!

to do gene exp summary, the geneExpression tw.q.mode should be continous by default so as to show violins.

the