Fix crash if no devices.

plugins/feature/sid/sidaddchannelsdialog.cpp

@@ -82,6 +82,8 @@ SIDAddChannelsDialog::~SIDAddChannelsDialog()
 }
 
 void SIDAddChannelsDialog::accept()
+{
+    if (ui->channels->columnCount() > 2)
     {
         MainCore *mainCore = MainCore::instance();
         connect(mainCore, &MainCore::channelAdded, this, &SIDAddChannelsDialog::channelAdded);
@@ -91,6 +93,11 @@ void SIDAddChannelsDialog::accept()
         m_col = COL_DEVICE;
         addNextChannel();
     }
+    else
+    {
+        QDialog::accept();
+    }
+}
 
 void SIDAddChannelsDialog::addNextChannel()
 {