[clang-tools-extra] [NFC] Fix potential underflow constant. (PR #118528)

[Aaron Ballman via cfe-commits]

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@@ -58,10 +58,10 @@ getDerivedParameter(const ClassTemplateSpecializationDecl *CRTP,
                Arg.getAsType()->getAsCXXRecordDecl() == Derived;
       });
 
-  return AnyOf ? CRTP->getSpecializedTemplate()
-                     ->getTemplateParameters()
-                     ->getParam(Idx - 1)
-               : nullptr;
+  return AnyOf && Idx > 0 ? CRTP->getSpecializedTemplate()
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AaronBallman wrote:

If the range is empty, then `Idx` is not incremented, but `AnyOf` will be false.

https://github.com/llvm/llvm-project/pull/118528