hgweb: do not use unassigned variables in exception handling

mercurial/hgweb/webcommands.py

@@ -53,12 +53,11 b' def rawfile(web, req, tmpl):'
 
 def file(web, req, tmpl):
     path = web.cleanpath(req.form.get('file', [''])[0])
-    if path:
+    if not path:
+        return web.manifest(tmpl, web.changectx(req), path)
         try:
             return web.filerevision(tmpl, web.filectx(req))
         except revlog.LookupError, inst:
-            pass
-
     try:
         return web.manifest(tmpl, web.changectx(req), path)
     except ErrorResponse: