Give the correct error when the conversion is skipped due to the temp file already existing.

refactor_music_library.sh

@@ -268,20 +268,24 @@ find "$OLD_DIR" -type f ! -name "*".$EXT | sort | while read non_mp3; do
 	temp_file="$INT_DIR/${temp_file//[^[:alnum:][:space:].]/}.$EXT"
 	echo "temp_file='$temp_file'"
 
-	status=""
-	if [[ ! -s "$temp_file" ]]; then
-		# Actual conversion.
-		ffmpeg -y \
-			-nostdin -hide_banner -loglevel quiet \
-			-i "$non_mp3" "$temp_file"
-		status="$?"
+	if [[ -s "$temp_file" ]]; then
+		echo "*** FAILED: Temporary file already exists!"
+		echo "**** Please remove any failed previous runs."
+		exit 1
 	fi
 
+	# Actual conversion.
+	status=""
+	ffmpeg -y \
+		-nostdin -hide_banner -loglevel quiet \
+		-i "$non_mp3" "$temp_file"
+	status="$?"
+
 	if [[ $status != 0 ]]; then
 		echo "*** FAILED: Exited with status '$status'."
 		echo "**** To troubleshoot, try running this:"
 		echo "ffmpeg -y -i \"$non_mp3\" \"$temp_file\""
-		exit
+		exit 1
 	fi
 	echo "*** Success!"