Fix some misc. frontend correctness bugs

frontend/src/components/MapView.tsx

@@ -131,9 +131,23 @@ export function MapView({ contacts, focusedKey }: MapViewProps) {
 
   // Store ref for a marker
   const setMarkerRef = useCallback((key: string, ref: LeafletCircleMarker | null) => {
+    if (ref === null) {
+      delete markerRefs.current[key];
+      return;
+    }
+
     markerRefs.current[key] = ref;
   }, []);
 
+  useEffect(() => {
+    const currentKeys = new Set(mappableContacts.map((contact) => contact.public_key));
+    for (const key of Object.keys(markerRefs.current)) {
+      if (!currentKeys.has(key)) {
+        delete markerRefs.current[key];
+      }
+    }
+  }, [mappableContacts]);
+
   // Open popup for focused contact after map is ready
   useEffect(() => {
     if (focusedContact && markerRefs.current[focusedContact.public_key]) {

frontend/src/components/MessageList.tsx

@@ -373,7 +373,22 @@ export function MessageList({
       }
     }
 
-    setResendableIds(newResendable);
+    setResendableIds((prev) => {
+      if (prev.size === newResendable.size) {
+        let changed = false;
+        for (const id of newResendable) {
+          if (!prev.has(id)) {
+            changed = true;
+            break;
+          }
+        }
+        if (!changed) {
+          return prev;
+        }
+      }
+
+      return newResendable;
+    });
 
     return () => {
       for (const timer of timers.values()) clearTimeout(timer);