Client - display page error if can not fetch app config

fittrackee_client/src/locales/en/api.json

@@ -2,6 +2,7 @@
   "ERROR": {
     "UNKNOWN": "Error. Please try again or contact the administrator.",
     "Invalid credentials": "Invalid credentials.",
+    "Network Error": "Network Error",
     "Password and password confirmation don't match": "Password and password confirmation don't match.",
     "Password: 8 characters required": "Password: 8 characters required.",
     "Username: 3 to 12 characters required": "Username: 3 to 12 characters required.",