Don't show "Welcome to GitLab" when the search didn't return any projects

Rémy Coutablerequested to merge
fix/13785-dashboard-projects-display-welcome-after-search into master

Fixes #13785 (closed). /cc @pixdrift

Before

Screen_Shot_2016-03-02_at_10.55.02

After

Screen_Shot_2016-03-02_at_12.12.33

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