[clang-tools-extra] [clang-tidy][NFC] Enable `bugprone-unchecked-optional-access` in `clang-tidy` config and fix warnings (PR #170004)

[Baranov Victor via cfe-commits]

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@@ -304,6 +304,9 @@ static bool isQualificationConvertiblePointer(QualType From, QualType To,
            "From pointer or array has no pointee or element!");
     assert(ToPointeeOrElem && "To pointer or array has no pointee or element!");
 
+    if (!FromPointeeOrElem || !ToPointeeOrElem)
+      return false;
+
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vbvictor wrote:

If we aren't enabling this check in CI, we better use just `assert` without any `if` statements.

https://github.com/llvm/llvm-project/pull/170004