Only allow expand shields when there are blocked items

[srirambv]

Description

Details view open for 0 blocked items on shields

Steps to Reproduce

1. Install beta build
2. Visit https://brave.com
3. Click on shields, click on down carrot, doesn't open the details view, cursor changes to hand icon
4. Click on 0, opens details view even though there is nothing to show

Actual result:

Expected result:

Should only change cursor to hand icon when there are blocked items so that the details view can be shown

Reproduces how often:

Easy

Brave version (brave://version info)

Brave	0.56.7 Chromium: 70.0.3538.77 (Official Build) beta (64-bit)
Revision	0f6ce0b0cd63a12cb4eccea3637b1bc9a29148d9-refs/branch-heads/3538@{#1039}
OS	All

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds?
  Yes on beta

Website problems only:

• Does the issue resolve itself when disabling Brave Shields?
• Is the issue reproducible on the latest version of Chrome?

Additional Information

Follow up to #507
cc: @karenkliu @tomlowenthal

[bsclifton]

Updated to be 0.58.x after DEPS was updated with brave/brave-core#820

PR is tagged with uplift-request; let's make sure to modify milestone if that is approved 😄

[GeetaSarvadnya]

Verification Passed on

Brave	0.57.12 Chromium: 71.0.3578.75 (Official Build) (64-bit)
Revision	06ef00b5279f93f8e0c1e73acedd49d7dcc09767-refs/branch-heads/3578@{#836}
OS	Windows

• Verified the STR mentioned in the issue.

Verified passed with

Brave	0.57.12 Chromium: 71.0.3578.75 (Official Build) (64-bit)
Revision	06ef00b5279f93f8e0c1e73acedd49d7dcc09767-refs/branch-heads/3578@{#836}
OS	Mac OS X

• Verified STR in issue

Verification passed on

Brave	0.57.17 Chromium: 71.0.3578.80 (Official Build) (64-bit)
Revision	2ac50e7249fbd55e6f517a28131605c9fb9fe897-refs/branch-heads/3578@{#860}
OS	Linux