fix decrement handling

repertory/librepertory/src/file_manager/ring_buffer_base.cpp

@@ -327,7 +327,8 @@ void ring_buffer_base::reader_thread(bool is_forward) {
       if (next_chunk > ring_end_) {
         next_chunk = ring_pos_;
       }
-    } else if (last_marker != ring_begin_) {
+    } else {
+      if (last_marker != ring_begin_) {
         last_marker = ring_begin_;
         next_chunk = ring_pos_;
       }
@@ -335,6 +336,7 @@ void ring_buffer_base::reader_thread(bool is_forward) {
       if (next_chunk > ring_begin_) {
         --next_chunk;
       }
+    }
 
     if (read_state_[next_chunk % read_state_.size()]) {
       if (get_stop_requested()) {