Added another bound check in on_debugStep_triggered() to prevent the debugger from trying to move forward (e.g. if you hit F10) in case we are already at the end

alethzero/MainWin.cpp

@@ -1517,6 +1517,7 @@ void Main::on_create_triggered()
 
 void Main::on_debugStep_triggered()
 {
+	if (ui->debugTimeline->value() < m_history.size()) {
 		auto l = m_history[ui->debugTimeline->value()].levels.size();
 		if ((ui->debugTimeline->value() + 1) < m_history.size() && m_history[ui->debugTimeline->value() + 1].levels.size() > l)
 		{
@@ -1526,6 +1527,7 @@ void Main::on_debugStep_triggered()
 		}
 		else
 			on_debugStepInto_triggered();
+	}
 }
 
 void Main::on_debugStepInto_triggered()