Fix display of current position in an audio-only recording.

Once the decoder drains, we fake-increment the frame count so the
current position looks reasonable in the OSD, rather than appearing to
stall.  Refs #11357.

mythtv/libs/libmythtv/mythplayer.cpp

@@ -2393,6 +2393,8 @@ bool MythPlayer::VideoLoop(void)
 
     if (FlagIsSet(kVideoIsNull) && decoder)
         decoder->UpdateFramesPlayed();
+    else if (decoder && decoder->GetEof() != kEofStateNone)
+        ++framesPlayed;
     else
         framesPlayed = videoOutput->GetFramesPlayed();
     return !IsErrored();