Fix: Debugger does not show undefined factSet any more

src/Debugger.svelte

@@ -28,7 +28,7 @@
       .flat();
     // Deduplicate entries
     const factsSet = new Set(allFacts);
-    return [...factsSet];
+    return [...factsSet].filter(e => e !== undefined);
   }
 
   let seenFactIds = new Set<String>([
@@ -93,6 +93,7 @@
       addFactInputValue = "";
     }}>Add</button
   >
+  <button style="width: 13rem;" on:click={() => gameFactsStore.set([])}>Reset facts</button>
 </div>
 
 <style>