message: Disable previous/next buttons when there's no previous/next drawcall
diff: @@ -398,6 +398,11 @@ void EventBrowser::on_events_currentItemChanged(RDTreeWidgetItem *current, RDTre
  m_Ctx.SetEventID({this}, tag.EID, tag.lastEID);
  + const DrawcallDescription *draw = m_Ctx.GetDrawcall(tag.lastEID);
  +
  + ui->stepPrev->setEnabled(draw && draw->previous);
  + ui->stepNext->setEnabled(draw && draw->next);
  +
  highlightBookmarks();
  }
  @@ -490,7 +495,7 @@ void EventBrowser::on_findPrev_clicked()
  void EventBrowser::on_stepNext_clicked()
  {
  - if(!m_Ctx.LogLoaded())
  + if(!m_Ctx.LogLoaded() || !ui->stepNext->isEnabled())
  return;
  const DrawcallDescription *draw = m_Ctx.CurDrawcall();
  @@ -501,7 +506,7 @@ void EventBrowser::on_stepNext_clicked()
  void EventBrowser::on_stepPrev_clicked()
  {
  - if(!m_Ctx.LogLoaded())
  + if(!m_Ctx.LogLoaded() || !ui->stepPrev->isEnabled())
  return;
  const DrawcallDescription *draw = m_Ctx.CurDrawcall();
  