AC_Avoidance: check for alloc failure of ObjectBuffer

libraries/AC_Avoidance/AP_OADatabase.cpp

@@ -187,6 +187,11 @@ void AP_OADatabase::init_queue()
     }
 
     _queue.items = new ObjectBuffer<OA_DbItem>(_queue.size);
+    if (_queue.items != nullptr && _queue.items->get_size() == 0) {
+        // allocation failed
+        delete _queue.items;
+        _queue.items = nullptr;
+    }
 }
 
 void AP_OADatabase::init_database()