Fix crash when pTargetMD is null

[thaystg]

pTargetMD can be null here, so checking pTargetMD before accessing it.

Side effect of: #110334

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[thaystg]

/backport to release/8.0-staging

[thaystg]

/backport to release/9.0-staging

[github-actions]

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/12297696742

[github-actions]

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/12297698622

[mikelle-rogers]

I don't know if that is the needed fix. After investigating last night, I found that before the change, my code went through the first branch in IsTailCallThatReturns. This was because the if statement was if (pTailCallDispatcherMD == NULL). With the fix, there has been an addition to that first if statement and it now reads if (pTailCallDispatcherMD == NULL && type == TailCallFunctionType::TailCallThatReturns), which makes it so my code no longer goes down that first branch.

I will test it, and let you know what happens, and if I think we need to have some more investigation/discussion regarding this issue.