Update src/io/rsm/raft.hpp

Co-authored-by: János Benjamin Antal <antaljanosbenjamin@users.noreply.github.com>

src/io/rsm/raft.hpp

@@ -372,15 +372,16 @@ class Raft {
 
   LogIndex LastLogIndex() { return state_.log.size(); }
 
-  Term LastLogTerm() {
+  Term LastLogTerm() const {
     if (state_.log.empty()) {
       return 0;
     }
 
-    auto &[term, data] = state_.log.back();
+    const auto &[term, data] = state_.log.back();
     return term;
   }
 
+
   template <typename... Ts>
   void Log(Ts &&...args) {
     const Time now = io_.Now();