Fix: Dereference after NULL check in consumer

Fix: Dereference after NULL check in consumer

Dereference after NULL check in consumer discarded events/lost packets
commands.

Found by Coverity:

CID 1040158 (#1 of 2): Dereference after null check (FORWARD_NULL)24.
var_deref_op: Dereferencing null pointer channel.

CID 1040158 (#2 of 2): Dereference after null check (FORWARD_NULL)24.
var_deref_op: Dereferencing null pointer channel.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>