[clang] [NFC][analyzer] Refactor Environment to map Expr to SVal instead of Stmt to SVal (PR #193295)

[Balázs Benics via cfe-commits]

================
@@ -64,7 +64,9 @@ void UndefBranchChecker::checkBranchCondition(const Stmt *Condition,
   // ObjCForCollection is a loop, but has no actual condition.
   if (isa<ObjCForCollectionStmt>(Condition))
     return;
-  if (!Ctx.getSVal(Condition).isUndef())
+
+  const Expr *Ex = dyn_cast<Expr>(Condition);
----------------
steakhal wrote:

```suggestion
  const auto *Ex = cast<Expr>(Condition);
```

https://github.com/llvm/llvm-project/pull/193295