prevent exception in admin, thanks Marin

VERSION

@@ -1 +1 @@
-Version 2.0.6 (2012-09-04 14:43:30) stable
+Version 2.0.6 (2012-09-04 14:47:09) stable

applications/admin/controllers/default.py

@@ -249,6 +249,10 @@ def site():
             fname = request.vars.file.filename
             f = request.vars.file.file
             
+        else:
+            session.flash = 'No file uploaded and no URL specified'
+            redirect(URL(r=request))
+
         if f:
             appname = cleanpath(form_update.vars.name)
             installed = app_install(appname, f,