System: Don't try to read SYSTEM.CNF from Audio CD

src/core/system.cpp

@@ -1086,8 +1086,11 @@ DiscRegion System::GetRegionFromSystemArea(CDImage* cdi)
 {
   // The license code is on sector 4 of the disc.
   u8 sector[CDImage::DATA_SECTOR_SIZE];
-  if (!cdi->Seek(1, 4) || cdi->Read(CDImage::ReadMode::DataOnly, 1, sector) != 1)
+  if (cdi->GetTrackMode(1) == CDImage::TrackMode::Audio || !cdi->Seek(1, 4) ||
+      cdi->Read(CDImage::ReadMode::DataOnly, 1, sector) != 1)
+  {
     return DiscRegion::Other;
+  }
 
   static constexpr char ntsc_u_string[] = "          Licensed  by          Sony Computer Entertainment Amer  ica ";
   static constexpr char ntsc_j_string[] = "          Licensed  by          Sony Computer Entertainment Inc.";

src/util/iso_reader.cpp

@@ -29,6 +29,12 @@ bool IsoReader::Open(CDImage* image, u32 track_number, Error* error)
   m_image = image;
   m_track_number = track_number;
 
+  if (image->GetTrackMode(static_cast<u8>(track_number)) == CDImage::TrackMode::Audio)
+  {
+    Error::SetStringFmt(error, "Track {} is an audio track.", track_number);
+    return false;
+  }
+
   if (!ReadPVD(error))
     return false;