archrelease: Fix SVN error when repository is empty

If trash is empty, `svn rm -q "${trash[@]}"` fails with:

    svn: Try 'svn help' for more info and then
    svn: Not enough arguments provided

This doesn't result in any further malfunction but is kind of confusing
and unexpected. Skipping `svn rm` on an empty trash fixes this.

Reported-by: Alexander Rødseth <rodseth@gmail.com>
Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>

archrelease.in

@@ -46,7 +46,7 @@ for tag in "$@"; do
 		while read -r file; do
 			trash+=("repos/$tag/$file")
 		done < <(svn ls "repos/$tag")
-		svn rm -q "${trash[@]}"
+		[[ $trash ]] && svn rm -q "${trash[@]}"
 	else
 		mkdir -p "repos/$tag"
 		svn add --parents -q "repos/$tag"