remove redundant dashes in render filenames

lib/helpers.js

@@ -322,7 +322,7 @@ exp.get_render = function(rid, userId, scale, helm, body, callback) {
       callback(err, -1, skin_hash, null);
       return;
     }
-    var renderpath = path.join(__dirname, "..", config.renders_dir, [skin_hash, "-", scale, "-", get_type(helm, body)].join("-") + ".png");
+    var renderpath = path.join(__dirname, "..", config.renders_dir, [skin_hash, scale, get_type(helm, body)].join("-") + ".png");
     fs.exists(renderpath, function(exists) {
       if (exists) {
         renders.open_render(rid, renderpath, function(render_err, rendered_img) {