fix: add attribute hover style is not applied

[oltionchampari]

Closes https://github.com/Caleydo/cohort/issues/718

Developer Checklist (Definition of Done)

Issue

• All acceptance criteria from the issue are met
• Tested in latest Chrome/Firefox

UI/UX/Vis

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  • Reviewer(s) approve of concept and design

Code

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• Code is cleaned up and formatted
• Unit tests are written (frontend/backend if applicable)
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PR

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Summary of changes

• The error was a result of the event.currentTarget being null by the time the setTimeout is executed
• This fixes also the hover background on the gene when the gene datatype is hovered

Screenshots

before

after

Additional notes for the reviewer(s)

Thanks for creating this pull request 🤗

[keckelt]

It might not be necessary, but you can also use it on line 311.

[thinkh]

Line 311 only handles the case for non-genes. Ollie fixed the gene case here and the event might not be available after the timeout is executed. So I agree with the fix he proposed.

[thinkh]

The error is fixed with your changes.

[thinkh]

Line 311 only handles the case for non-genes. Ollie fixed the gene case here and the event might not be available after the timeout is executed. So I agree with the fix he proposed.