Fix StyledRangeStore Crash

[thecoolwinter]

Description

Fixes a potential crash with the styled range store. This is caused by a race condition where the store hasn't been notified of a content length change, but has been given new data to put in the (valid) range. This only happens when content is appended to the end of a document and comes into view at the same time. This is fixed by simply appending the missing range when updating the style storage object.

Related Issues

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Checklist

• I read and understood the contributing guide as well as the code of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots

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