Fix missing blank href attr on <a> links in searchkit angular

[artfulrobot]

Before

SK AngularJS generates 'links' without href attributes. This means that the browser does not identify the clickable thing as a link. This has accessibility and visual problems (e.g. mouse shows as caret not pointer)

After

Blank hrefs supported where there isn't an actual href. Browser treats the clickable content as links :

[civibot]

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[colemanw]

retest this please

[colemanw]

Change makes sense