It just shows the animation that gets usually shown when an outside process selects something in the hierarchy.
Could you upload a build where this bug is fixed? It will make testing the preview with more complex projects more comfortable. 
i think that started happening in normal 5.6 or 2017… quite annoying…
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For me, using 5.6.0f3, I have no problem with double clicking showing selected object in scene view, as well as tapping “F” with the mouse over scene view does the same thing. Maybe this is a bug specifically with the new 2017?
hmm… couldn’t make it happen right now in 2017, i thought i saw it before this beta, but could be wrong then…
*nevermind i guess its been there: Unity Issue Tracker - Double-clicking a hierarchy gameObject no longer focuses the scene onto it
** and seems to be fixed in the latest build*: Updated May 11th 2017*