Remote sessions are not assigned an executor

Description

Sometimes the agentic sessions are not picked at all and no executor is assigned to these sessions. An example session is this. There are a few other sessions in this project that have the same issue.

Steps to reproduce

1. Clone this project locally.
2. Push this project to an ultimate namespace with feature flags ai_experiment_sast_fp_detection and enable_vulnerability_fp_detection enabled.
3. Wait for the CI pipeline to finish.
4. Once the pipeline is finished navigate to Automate > Sessions, and observe that a couple of agentic sessions for SAST FP detection workflow are created.
5. There could be a probability that a few of these sessions have "Executor ID" as "N/A". These are the problematic sessions and these are never picked by any executor.

An example session - https://gitlab.com/compliance-group-testing-and-demos/demos/debug-issue-578824/-/automate/agent-sessions/1212886