server : fix restore for checkpoints with pos_min == 0 (ggml-org#21510)

Author: ggerganov

tools/server/server-context.cpp

@@ -2404,7 +2404,7 @@ struct server_context_impl {
                                             // guarantee that a checkpoint will result in at least one token being processed [TAG_PROMPT_LOGITS]
                                             LOG_INF("slot %12.*s: id %2d | task %d | Checking checkpoint with [%d, %d] against %d...\n", 12,
                                                 func_name, (slot).id, ((slot).task ? (slot).task->id : -1), cur.pos_min, cur.pos_max, pos_min_thold);
-                                            return cur.pos_min < pos_min_thold;
+                                            return cur.pos_min < pos_min_thold || cur.pos_min == 0;
                                         }
                                     );