Merge #402: gui: do not check empty addresses for duplicates

f508d4a1ce9739af92b99be479dcfeeda2d263d9 gui: do not check empty addresses for duplicates (jp1ac4)

Pull request description:

  This is to resolve #190.

  The check for a duplicate is skipped if the recipient address is an empty string.

  I was able to run the GUI locally and it seemed to work as required.

ACKs for top commit:
  edouardparis:
    ACK f508d4a1ce9739af92b99be479dcfeeda2d263d9

Tree-SHA512: 32a1fc89eba7fd0f8bb39d19ec76957228e0a4240d0d784c35890ecea8e0f8540c529001cda3d81380b9fa24547325fb1ea2b0d7db82e0facf9fc8e10d7ed775

gui/src/app/state/spend/step.rs

@@ -77,7 +77,7 @@ impl ChooseRecipients {
             if !recipient.valid() {
                 self.is_valid = false;
             }
-            if !self.is_duplicate {
+            if !self.is_duplicate && !recipient.address.value.is_empty() {
                 self.is_duplicate = self.recipients[..i]
                     .iter()
                     .any(|r| r.address.value == recipient.address.value);