Prevent DXRenderer from using invalid properties

[skyline75489]

Summary of the Pull Request

The working fix, in case you needed it.

References

PR Checklist

• Closes Crashes if zoom font size up and down rapidly with ctrl + scroll wheel #5479
• CLA signed. If not, go over here and sign the CLA
• Tests added/passed
• Requires documentation to be 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

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

Manually validated.

[miniksa]

It's a quick and easy fix, but it's just hiding the problem. It shouldn't be possible to pull those state variables out from under the renderer while it is in the middle of a frame. That's an assumption the entire renderer makes. So we shouldn't fix this with just a null check as it'll just bounce around to somewhere else.

I'd rather we fix this with doing the correct locking per what @zadjii-msft mentioned in #5479.

[skyline75489]

Close this in favor of whatever @zadjii-msft will offer. I'm pretty sure it'll be good.