growth: Fix no conditions

Fix the case that there is no `conditions` in the config.

Bug: b:332618322 b:332411721
Test: manually tested. Will add tests in follow ups.
Change-Id: I6a80b40ce85d8c565a739b56d3450e108475d780
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5426494


Commit-Queue: Tao Wu <wutao@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Li Lin <llin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283526}