Check for null callback pointers in the
Vendor HAL AIDL callback util.

Bug: 376249464
Test: m
Change-Id: Ifd48b8d9ba81ce5b59d3a3ea39667390a688bb53
diff --git a/wifi/aidl/default/aidl_callback_util.h b/wifi/aidl/default/aidl_callback_util.h
index f8ba53b..2419db9 100644
--- a/wifi/aidl/default/aidl_callback_util.h
+++ b/wifi/aidl/default/aidl_callback_util.h
@@ -45,6 +45,11 @@
     ~AidlCallbackHandler() { invalidate(); }
 
     bool addCallback(const std::shared_ptr<CallbackType>& cb) {
+        if (cb == nullptr) {
+            LOG(ERROR) << "Unable to register a null callback";
+            return false;
+        }
+
         std::unique_lock<std::mutex> lk(callback_handler_lock_);
         void* cbPtr = reinterpret_cast<void*>(cb->asBinder().get());
         const auto& cbPosition = findCbInSet(cbPtr);