Fix form handling for user feedback

issue was noticed on demo site, but possibly existed elsewhere?  also not 100%
sure about this fix, but it's believed to be okay...

tailbone/static/themes/falafel/js/tailbone.feedback.js

@@ -27,8 +27,13 @@ let FeedbackForm = {
             }
 
             this.$http.post(this.action, params, {headers: headers}).then(({ data }) => {
-                this.showDialog = false
-                alert("Message successfully sent.\n\nThank you for your feedback.")
+                if (data.ok) {
+                    alert("Message successfully sent.\n\nThank you for your feedback.")
+                    this.showDialog = false
+                } else {
+                    alert("Sorry!  Your message could not be sent.\n\n"
+                          + "Please try to contact the site admin some other way.")
+                }
             })
         },
     }