Fix: flt.lttng-utils.debug-info: Dereference after null check

Coverity report:
  CID 1401218 (#1 of 1): Dereference after null check (FORWARD_NULL)
  4. var_deref_op: Dereferencing null pointer bin.

Reported-by: Coverity (1401218) Dereference after null check
Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: I1821a4f2e39096cb3dca75033ab9ce25f4b63127
Reviewed-on: https://review.lttng.org/c/babeltrace/+/2167
Reviewed-by: Simon Marchi <simon.marchi@efficios.com>
CI-Build: Simon Marchi <simon.marchi@efficios.com>
Tested-by: jenkins <jenkins@lttng.org>