Don't throw on empty intra-process buffer

Author: Mauro Passerino

rclcpp/include/rclcpp/experimental/buffers/ring_buffer_implementation.hpp

@@ -75,7 +75,7 @@ class RingBufferImplementation : public BufferImplementationBase<BufferT>
 
     if (!has_data()) {
       RCLCPP_ERROR(rclcpp::get_logger("rclcpp"), "Calling dequeue on empty intra-process buffer");
-      throw std::runtime_error("Calling dequeue on empty intra-process buffer");
+      return BufferT();
     }
 
     auto request = std::move(ring_buffer_[read_index_]);

rclcpp/include/rclcpp/experimental/subscription_intra_process.hpp

@@ -159,7 +159,9 @@ class SubscriptionIntraProcess : public SubscriptionIntraProcessBase
 
     if (any_callback_.use_take_shared_method()) {
       ConstMessageSharedPtr msg = buffer_->consume_shared();
-      any_callback_.dispatch_intra_process(msg, msg_info);
+      if(msg != nullptr) {
+        any_callback_.dispatch_intra_process(msg, msg_info);
+      }
     } else {
       MessageUniquePtr msg = buffer_->consume_unique();
       any_callback_.dispatch_intra_process(std::move(msg), msg_info);