[FIX] website_google_map: do not allow invalid partner prefix

The only supported prefixes are the following:
 - /partners/ when website_partner and/or website_crm_partner_assign are installed
 - /customers/ when website_customer is installed

addons/website_google_map/controllers/main.py

@@ -57,9 +57,14 @@ class google_map(http.Controller):
                 'longitude': escape(str(partner.partner_longitude)),
                 })
 
+        if 'customers' in post.get('partner_url', ''):
+            partner_url = '/customers/'
+        else:
+            partner_url = '/partners/'
+
         # generate the map
         values = {
-            'partner_url': post.get('partner_url'),
+            'partner_url': partner_url,
             'partner_data': json.dumps(partner_data)
         }
         return request.website.render("website_google_map.google_map", values)