title: Keys must be non-empty strings and can't contain ".", "#", "$", "/", "[", or "]"
body: <p>I am trying to write with admin permission two places at once on firebase functions.
  Getting this strange error:</p>
  
  <blockquote>
    <p>Error: Firebase.set failed: First argument  contains an invalid key (/Auction/TD6MKEhS/-Kn9cMUPkk) </p>
  </blockquote>
  
  <p>My code is:</p>
  
  <pre><code>var newPostRef = admin.database().ref().child("History/" + this.customeruid + '/' + this.quoteid + '/' + this.banuid).push();
  var newPostKey = newPostRef.key;
  var updatedBidQuote = {};
  // Create the data we want to update
  let postData = { creationBidDate: admin.database.ServerValue.TIMESTAMP, customeruid: this.banuid, quoteCompanyCreatoruid: this.customeruid, Amount: this.banBid };
  updatedBidQuote['/Auction/' + this.customeruid + '/' + this.quoteid] = postData;
  updatedBidQuote['/History/' + this.customeruid + '/' + this.quoteid + '/' + this.banuid + '/' + newPostKey] = postData;
  return admin.database().ref().set(updatedBidQuote);
  </code></pre>
  
  <p>I check the object of postData and didnt have any (.keys or strange value)</p>