message: Check that all states are present before allowing any stepping
diff: @@ -1324,7 +1324,7 @@ void ShaderViewer::on_watch_itemChanged(QTableWidgetItem *item)
  bool ShaderViewer::stepBack()
  {
  - if(!m_Trace)
  + if(!m_Trace || m_States.empty())
  return false;
  if(IsFirstState())
  @@ -1378,7 +1378,7 @@ bool ShaderViewer::stepBack()
  bool ShaderViewer::stepNext()
  {
  - if(!m_Trace)
  + if(!m_Trace || m_States.empty())
  return false;
  if(IsLastState())
  @@ -1417,7 +1417,7 @@ bool ShaderViewer::stepNext()
  void ShaderViewer::runToCursor()
  {
  - if(!m_Trace)
  + if(!m_Trace || m_States.empty())
  return;
  ScintillaEdit *cur = currentScintilla();
  @@ -1529,7 +1529,7 @@ void ShaderViewer::run()
  void ShaderViewer::runTo(QVector<size_t> runToInstruction, bool forward, ShaderEvents condition)
  {
  - if(!m_Trace)
  + if(!m_Trace || m_States.empty())
  return;
  bool firstStep = true;
  