After unsuccessfull search is now text cleared. Useful for barcode scanners. closes #299

shop/shopform.cpp

@@ -512,4 +512,5 @@ void ShopForm::on_commoditySearch_returnPressed()
         ShopItemPtr item = m_commodityModel->itemFromIndex(ui->commodityTable->currentIndex());
         addItem(item, ui->spnCount->value());
     }
+    ui->commoditySearch->clear();
 }