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## Summary of the Pull Request
Adds a negative value check for when the terminal window is hidden/show in VS
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## References
[Bug 1265984](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1265984): [Terminal] VS crashes when clicking the hidden terminal tab
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## PR Checklist
* [ ] Closes #xxx
* [ ] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx
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## Detailed Description of the Pull Request / Additional comments
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## Validation Steps Performed
Manual validation.
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