[resultui] Prevent undefined tooltips from appearing.
[resultui] Prevent undefined tooltips from appearing.

Change-Id: Ib12a152f150342aaa31380a7c4968a8b937d3fc6
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2537289
Reviewed-by: Weiwei Lin <968518a24f41fef00b747498600e52b792d06ae0@google.com>
Commit-Queue: Joey Scarr <e609d4c46132d2dea94acf5ac2b9f229ffc1f245@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go