[Qt] coin control change address handling update

- re-work change address handling so that default is CNoDestination(),
  until a verified and known change address was entered (easier code flow)
- add a missing NULL pointer check for adresstablemodel
- add a missing text when opening coin control address selection for
  priority and ensure the label is black
- add a missing . at the end of a sentence

src/qt/coincontroldialog.cpp

@@ -449,7 +449,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
         }
     }
 
-    QString sPriorityLabel      = "";
+    QString sPriorityLabel      = tr("none");
     int64_t nAmount             = 0;
     int64_t nPayFee             = 0;
     int64_t nAfterFee           = 0;
@@ -594,7 +594,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
 
     // turn labels "red"
     l5->setStyleSheet((nBytes >= 1000) ? "color:red;" : "");                            // Bytes >= 1000
-    l6->setStyleSheet((!AllowFree(dPriority)) ? "color:red;" : "");         // Priority < "medium"
+    l6->setStyleSheet((dPriority > 0 && !AllowFree(dPriority)) ? "color:red;" : "");    // Priority < "medium"
     l7->setStyleSheet((fLowOutput) ? "color:red;" : "");                                // Low Output = "yes"
     l8->setStyleSheet((nChange > 0 && nChange < CENT) ? "color:red;" : "");             // Change < 0.01BTC
 
@@ -604,7 +604,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     toolTip1 += tr("Can vary +/- 1 byte per input.");
 
     QString toolTip2 = tr("Transactions with higher priority are more likely to get included into a block.") + "<br /><br />";
-    toolTip2 += tr("This label turns red, if the priority is smaller than \"medium\"") + "<br /><br />";
+    toolTip2 += tr("This label turns red, if the priority is smaller than \"medium\".") + "<br /><br />";
     toolTip2 += tr("This means a fee of at least %1 per kB is required.").arg(BitcoinUnits::formatWithUnit(nDisplayUnit, CTransaction::nMinTxFee));
 
     QString toolTip3 = tr("This label turns red, if any recipient receives an amount smaller than %1.").arg(BitcoinUnits::formatWithUnit(nDisplayUnit, CENT)) + "<br /><br />";

src/qt/sendcoinsdialog.cpp

@@ -546,44 +546,45 @@ void SendCoinsDialog::coinControlChangeChecked(int state)
 // Coin Control: custom change address changed
 void SendCoinsDialog::coinControlChangeEdited(const QString& text)
 {
-    if (model)
+    if (model && model->getAddressTableModel())
     {
-        CoinControlDialog::coinControl->destChange = CBitcoinAddress(text.toStdString()).Get();
+        // Default to no change address until verified
+        CoinControlDialog::coinControl->destChange = CNoDestination();
+        ui->labelCoinControlChangeLabel->setStyleSheet("QLabel{color:red;}");
 
-        // label for the change address
+        CBitcoinAddress addr = CBitcoinAddress(text.toStdString());
-        ui->labelCoinControlChangeLabel->setStyleSheet("QLabel{color:black;}");
+
-        if (text.isEmpty())
+        if (text.isEmpty()) // Nothing entered
+        {
             ui->labelCoinControlChangeLabel->setText("");
-        else if (!CBitcoinAddress(text.toStdString()).IsValid())
+        }
+        else if (!addr.IsValid()) // Invalid address
         {
-            // invalid change address
-            CoinControlDialog::coinControl->destChange = CNoDestination();
-
             ui->lineEditCoinControlChange->setValid(false);
-            ui->labelCoinControlChangeLabel->setStyleSheet("QLabel{color:red;}");
             ui->labelCoinControlChangeLabel->setText(tr("Warning: Invalid Bitcoin address"));
         }
-        else
+        else // Valid address
-        {
-            QString associatedLabel = model->getAddressTableModel()->labelForAddress(text);
-            if (!associatedLabel.isEmpty())
-                ui->labelCoinControlChangeLabel->setText(associatedLabel);
-            else
         {
             CPubKey pubkey;
             CKeyID keyid;
-                CBitcoinAddress(text.toStdString()).GetKeyID(keyid);
+            addr.GetKeyID(keyid);
-                if (model->getPubKey(keyid, pubkey))
+            if (!model->getPubKey(keyid, pubkey)) // Unknown change address
-                    ui->labelCoinControlChangeLabel->setText(tr("(no label)"));
-                else
             {
-                    // unknown change address
-                    CoinControlDialog::coinControl->destChange = CNoDestination();
-
                 ui->lineEditCoinControlChange->setValid(false);
-                    ui->labelCoinControlChangeLabel->setStyleSheet("QLabel{color:red;}");
                 ui->labelCoinControlChangeLabel->setText(tr("Warning: Unknown change address"));
             }
+            else // Known change address
+            {
+                ui->labelCoinControlChangeLabel->setStyleSheet("QLabel{color:black;}");
+
+                // Query label
+                QString associatedLabel = model->getAddressTableModel()->labelForAddress(text);
+                if (!associatedLabel.isEmpty())
+                    ui->labelCoinControlChangeLabel->setText(associatedLabel);
+                else
+                    ui->labelCoinControlChangeLabel->setText(tr("(no label)"));
+
+                CoinControlDialog::coinControl->destChange = addr.Get();
             }
         }
     }