[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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@@ -96,6 +96,8 @@ void TimeSubtractionCheck::registerMatchers(MatchFinder *Finder) {
     const std::string TimeInverse = (llvm::Twine("ToUnix") + ScaleName).str();
     std::optional<DurationScale> Scale = getScaleForTimeInverse(TimeInverse);
     assert(Scale && "Unknown scale encountered");
+    if (!Scale)
+      continue;
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vbvictor wrote:

Can we then remove first `assert` if we still check via `if` later? (but preserve comment)

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