DevTools: fix bug with autocomplete without suggestion

`applySuggestion()` used to accept an empty string as suggestion, so
`_currentSuggestion` always had a length. After a recent transition
from strings to '?UI.SuggestBox.Suggestion', we need to check that
`_currentSuggestion` is not null when using it.

Bug: none
Change-Id: I4db14c47346b6318a03d1b73ef651bccc1e7038a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1536603
Commit-Queue: Erik Luo <luoe@chromium.org>
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643712}
1 file changed