context : clear sets containing encoder output sequence ids before storing new values (#12470)

Co-authored-by: Stanisław Szymczyk <sszymczy@gmail.com>

src/llama-context.cpp

@@ -1153,6 +1153,7 @@ int llama_context::encode(llama_batch & inp_batch) {
         // remember the sequence ids used during the encoding - needed for cross attention later
         cross.seq_ids_enc.resize(n_tokens);
         for (int32_t i = 0; i < n_tokens; i++) {
+            cross.seq_ids_enc[i].clear();
             for (int s = 0; s < ubatch.n_seq_id[i]; s++) {
                 llama_seq_id seq_id = ubatch.seq_id[i][s];
                 cross.seq_ids_enc[i].insert(seq_id);