DevTools: Fix IndexedDB inspection when resources panel is the first one to be selected.

BUG=408009
NOTRY=true

Review URL: https://codereview.chromium.org/509983002

git-svn-id: svn://svn.chromium.org/blink/trunk@181016 bbb929c8-8fbe-4397-9dbb-9b2b20218538