when on testnet, set testnet icon for about dialog

- add a comment

src/qt/bitcoingui.cpp

@@ -345,6 +345,7 @@ void BitcoinGUI::setClientModel(ClientModel *clientModel)
     this->clientModel = clientModel;
     if(clientModel)
     {
+        // Replace some strings and icons, when using the testnet
         if(clientModel->isTestNet())
         {
             setWindowTitle(windowTitle() + QString(" ") + tr("[testnet]"));
@@ -360,6 +361,8 @@ void BitcoinGUI::setClientModel(ClientModel *clientModel)
                 trayIcon->setIcon(QIcon(":/icons/toolbar_testnet"));
                 toggleHideAction->setIcon(QIcon(":/icons/toolbar_testnet"));
             }
+
+            aboutAction->setIcon(QIcon(":/icons/toolbar_testnet"));
         }
 
         // Keep up to date with client