[Clang] Assert non-null enum definition in CGDebugInfo::CreateTypeDefinition(const EnumType*) (llvm#105556)

This commit adds an assert to check for a non-null enum definition in
CGDebugInfo::CreateTypeDefinition(const EnumType*), ensuring
precondition validity.

Previous discussion on llvm#97105

Author: smanna12

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -3561,6 +3561,7 @@ llvm::DIType *CGDebugInfo::CreateTypeDefinition(const EnumType *Ty) {
 
   SmallVector<llvm::Metadata *, 16> Enumerators;
   ED = ED->getDefinition();
+  assert(ED && "An enumeration definition is required");
   for (const auto *Enum : ED->enumerators()) {
     Enumerators.push_back(
         DBuilder.createEnumerator(Enum->getName(), Enum->getInitVal()));