New score not drawn unless a pan-drag is made

Steps to reproduce
1. Open up MuseScore, close default score.
2. Create new score for scratchş donţt touch anything until you get to the instruments selection dialog. I double-clicked piano, but other might make no difference.
3. Hit finish.

Actual result: you're presented what seems to be an "empty" canvas (and an empty navigator as well). If you hold your left mouse button and move a bit, the score is drawn, both in the canvas and navigator.

Expected result: the empty score should be drawn without any user interaction.

Notes: seems to have been introduced in r2830. My test box configuration is the same (see my previous issues).