Require torrent category creation to be explicit

src/base/bittorrent/torrenthandle.cpp

@@ -1214,10 +1214,8 @@ bool TorrentHandle::setCategory(const QString &category)
 {
     if (m_category != category) {
         if (!category.isEmpty()) {
-            if (!Session::isValidCategoryName(category)) return false;
-            if (!m_session->categories().contains(category))
-                if (!m_session->addCategory(category))
-                    return false;
+            if (!Session::isValidCategoryName(category) || !m_session->categories().contains(category))
+                return false;
         }
 
         QString oldCategory = m_category;

src/webui/api/torrentscontroller.cpp

@@ -811,6 +811,10 @@ void TorrentsController::setCategoryAction()
     const QString category {params()["category"].trimmed()};
     applyToTorrents(hashes, [category](BitTorrent::TorrentHandle *torrent)
     {
+        auto *session = BitTorrent::Session::instance();
+        const QStringList categories = session->categories().keys();
+        if (!categories.contains(category) && !session->addCategory(category))
+            throw APIError(APIErrorType::Conflict, tr("Unable to create category"));
         if (!torrent->setCategory(category))
             throw APIError(APIErrorType::Conflict, tr("Incorrect category name"));
     });