[analyzer] Engine: fix crash with SEH __leave keyword

MSVC has a `try-except` statement.
This statement could containt a `__leave` keyword, which is similar to
`goto` to the end of the try block. The semantic of this keyword is not
implemented.

We should at least parse such code without crashing.

https://docs.microsoft.com/en-us/cpp/cpp/try-except-statement?view=msvc-160

Patch By: AbbasSabra!

Reviewed By: steakhal

Differential Revision: https://reviews.llvm.org/D102280