Set empty query labels to wildcard '*' for proper graph display

• Handle empty/whitespace query labels
• Auto-set to '*' when label is blank
• Ensure consistent graph behavior
• Prevent invalid query states

lightrag_webui/src/components/graph/GraphLabels.tsx

@@ -94,7 +94,13 @@ const GraphLabels = () => {
     useGraphStore.getState().setTypeColorMap(new Map<string, string>())
 
     try {
-      const currentLabel = label
+      let currentLabel = label
+
+      // If queryLabel is empty, set it to '*'
+      if (!currentLabel || currentLabel.trim() === '') {
+        useSettingsStore.getState().setQueryLabel('*')
+        currentLabel = '*'
+      }
 
       if (currentLabel && currentLabel !== '*') {
         // Scenario 1: Has specific label, try to refresh current label