service: Check buffer exists before is_allowed_target_buffer check.
service: Check buffer exists before is_allowed_target_buffer check.

Producers may have a commit request in flight when the session is
destroyed, in which case we should abort silently instead in debug
builds.

Bug: 73828976
Bug: 120653127
Change-Id: I56e0a8dc85073a53e67805db2ba113c4c0f9cf63
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto