[clang] [NFC][analyzer] Improve tracking of the current Block & LocCtx (PR #185107)

[Gábor Horváth via cfe-commits]

Xazax-hun wrote:

Ok, if we can identify the program points where these members can be reset to null so we catch inconsistencies, I am fine with the new approach. 

https://github.com/llvm/llvm-project/pull/185107