web: guard ThreatMap against missing stats buckets

Handle absent byType/bySeverity in API responses to prevent runtime
Object.entries(undefined) crashes.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: vsilent

web/src/components/ThreatMap.tsx

@@ -36,15 +36,17 @@ const ThreatMap: React.FC = () => {
 
   const getTypeData = () => {
     if (!statistics) return [];
-    return Object.entries(statistics.byType).map(([name, value]) => ({
+    const byType = statistics.byType || {};
+    return Object.entries(byType).map(([name, value]) => ({
       name,
       value,
     }));
   };
 
   const getSeverityData = () => {
     if (!statistics) return [];
-    return Object.entries(statistics.bySeverity).map(([name, value]) => ({
+    const bySeverity = statistics.bySeverity || {};
+    return Object.entries(bySeverity).map(([name, value]) => ({
       name,
       value,
     }));