The triggering entry in the parallel-suspend path stored
se.Checkpoint into innerCheckpoints unconditionally, while
the sibling loop already guarded otherSE.Checkpoint != nil.
A nil entry would later cause restoreNestedSuspended to
dereference innerCP.AgentName and panic. Apply the same
guard so a malformed SuspendedError falls through to the
regular result-collection path instead of poisoning the
checkpoint map.
Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>