Don't diff files that don't exist

markdown/build-html.sh

@@ -15,7 +15,9 @@ for FILE in $BASEDIR/*.md; do
 	echo "$BASENAME -> $OUTNAME"
 	TEMP=$(tempfile --dir=$BASEDIR --mode=0644 --suffix=.tmp)
 	markdown $FILE > $TEMP
+	if [[ -e $OUTPATH ]]; then
 		diff -ud --color=always $OUTPATH $TEMP || true
+	fi
 	mv $TEMP $OUTPATH
 done