[clang] [Clang] Give empty template parameter mapping an empty MLTAL (PR #164051)

[Corentin Jabot via cfe-commits]

================
@@ -564,12 +564,17 @@ ExprResult ConstraintSatisfactionChecker::EvaluateAtomicConstraint(
 std::optional<MultiLevelTemplateArgumentList>
 ConstraintSatisfactionChecker::SubstitutionInTemplateArguments(
     const NormalizedConstraintWithParamMapping &Constraint,
-    MultiLevelTemplateArgumentList MLTAL,
-    llvm::SmallVector<TemplateArgument> &SubstitutedOuterMost) {
+    const MultiLevelTemplateArgumentList &MLTAL,
+    llvm::SmallVector<TemplateArgument> &SubstitutedOutermost) {
----------------
cor3ntin wrote:

Yup, I meant a separate pr for it (feel free to merge without review)

https://github.com/llvm/llvm-project/pull/164051