[Feature]: Ensure that objects are actually retrieved from the configuration

[eflumerf]

Description

In many SmartDaqApplication implementations, Queue Descriptor and Network Descriptor inputs are matched against what the application expects, with pointers to the expected descriptors being then used to create the connection objects that the application needs.

e.g.

const QueueDescriptor* fa_output_qdesc = nullptr;

for (auto rule : get_queue_rules()) {
  auto destination_class = rule->get_destination_class();
  if (destination_class == "FragmentAggregatorModule") {
    fa_output_qdesc = rule->get_descriptor();
  }
}

Whenever an object is retrieved from the configuration with a pattern like this, the pointer should be checked and a BadConf exception thrown if it is still nullptr. This prevents segmentation faults that are much harder to diagnose than a mismatch of configuration objects.

Potential impact radius

Small/Isolated

Reason for change

No response

Suggested implementations

No response

Testing suggestions

No response

Anything else?

No response

[gcrone]

In case anything falls through the cracks, ConfigObjectFactory methods should also validate their inputs and throw an exception rather than segfault.