修复选择数据源的问题

public/js/app.js

@@ -974,7 +974,9 @@
     try {
       const response = await fetch('/api/sources');
       const sources = await response.json();
-      dom.sourceCount.textContent = `${Array.isArray(sources) ? sources.length : 0} 个数据源`;
+      const sourcesArray = Array.isArray(sources) ? sources : [];
+      dom.sourceCount.textContent = `${sourcesArray.length} 个数据源`;
+      updateSourceFilterOptions(sourcesArray);
     } catch (err) {
       // ignore
     }