Fix "Save As" button persistence after navigating away from search

Steps To Reproduce:

1. In Web UI, navigate to default search from left-side Drawer panel
2. Input any value into a field and execute search ("Save As" button appears in top right)
3. Click on another Drawer Item (e.g. "Browse")

Expected result: "Save As" button is not visible until returning to Search page

Actual result: "Save As" button persists across navigating to varying Drawer Items, and clicking on the "Save As" button results in no action.

Noting that clicking on the topmost "Home" icon does result in the "Save As" icon disappearing because <nuxeo-home> is made visible as <nuxeo-search-page> is hidden.