bugfix for files not containing audios

to_opus/to_opus.sh

@@ -40,6 +40,8 @@ for file in **/*.@($extension); do
 	# array over the bitrates of all streams
 	readarray -t bitrates <<<"$(ffprobe -v error -select_streams a -show_entries stream=bit_rate -of compact=p=0:nk=1 "$file")"
 
+	if [[ ${#channels} == 0 ]]; then continue; fi
+
 	# set a channel dependend bitrate for every audio stream
 	# to use ffmpegs default just comment out this block
 	for ((index=0; index<${#channels[@]};index++)); do