fix(ebpf): avoid panic in UpdateKallsyms on missing dependency nodes

[geyslan]

1. Explain what the PR does

b734a92 fix(ebpf): avoid panic in UpdateKallsyms on missing dependency nodes

UpdateKallsyms iterated policy-selected event IDs and called GetEvent
without checking errors, so IDs present in the policy manager but absent
from the dependencies tree caused a nil EventNode dereference.

Handle GetEvent errors explicitly: treat ErrNodeNotFound as a no-op for
ksymbol collection, log unexpected errors at debug, and skip nil nodes
defensively.

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2. Explain how to test it

3. Other comments

[Copilot]

Pull request overview

This PR fixes a potential panic in Tracee’s eBPF kernel-symbols update path by making Tracee.UpdateKallsyms() resilient to policy-selected event IDs that are not present in the events dependencies tree.

Changes:

• Handle t.eventsDependencies.GetEvent(id) errors instead of ignoring them to avoid nil dereferences.
• Treat dependencies.ErrNodeNotFound as a no-op for ksymbol collection, and log unexpected errors at debug level.
• Add a defensive nil check before accessing the returned dependency node.

[trvll]

+1