Fix a rampant crash in TSFInputControl when opening new tabs

[zadjii-msft]

Summary of the Pull Request

We're deref'ing a null _terminal. Don't do that. This is a okay fix, mostly to stem the bleeding. @DHowett-MSFT's got a mind for a real fix to #4166, but this isn't it.

PR Checklist

• related to We're not sizing the drag handle correctly all the time; it cuts off parts of the window sometimes #4166
• I work here
• Tests added/passed
• [n/a] Requires documentation to be updated

[carlos-zamora]

THANK YOU

[ghost]

Hello @miniksa!

Because this pull request has the AutoMerge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

Do note that I've been instructed to only help merge pull requests of this repository that have been opened for at least 8 hours, a condition that will be fulfilled in about 3 hours 56 minutes. No worries though, I will be back when the time is right! 😉

p.s. you can customize the way I help with merging this pull request, such as holding this pull request until a specific person approves. Simply @mention me (@msftbot) and give me an instruction to get started! Learn more here.

[miniksa]

@msftbot wait 1 second

[ghost]

Hello @miniksa!

I think you told me that you want to delay the approval for a certain amount of time, but I am not confident that I have understood you correctly.

Please try rephrasing your instruction to me.

[miniksa]

@msftbot wait 1 minute

[ghost]

Hello @miniksa!

Because you've given me some instructions on how to help merge this pull request, I'll be modifying my merge approach. Here's how I understand your requirements for merging this pull request:

• I won't merge this pull request until after the UTC date Sat, 07 Mar 2020 03:19:36 GMT, which is in 1 minute

If this doesn't seem right to you, you can tell me to cancel these instructions and use the auto-merge policy that has been configured for this repository. Try telling me "forget everything I just told you".

[ghost]

🎉Windows Terminal Preview v0.10.761.0 has been released which incorporates this pull request.:tada:

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