tree abc761d4764cf9befaf03fd70deb1463c5771518
parent aa559a84157093f903d768be376edf129cfd4c5a
author Martin Fick <mfick@codeaurora.org> 1552077941 -0700
committer Martin Fick <mfick@codeaurora.org> 1564590730 -0600

Detect and handle non-existing tasks more explicitly.

Return NULL for non-existing tasks on fetch since nulls are already used
in the task tree for INVALID tasks.

Change-Id: I37ca30eec59d27f2a2505bd0a6246cec63142e07