The bug

When a player's display name/number format is updated for a scoreboard objective for which they don't have a score yet, it gets displayed as a 0 anyway. Trying to reset its display styles affects that behavior in no way.

Additionally, scoreboard objectives with no set value are displayed anyway in the sidebar, though it has not been modified since its creation.

To reproduce

1. Add a scoreboard objective using /scoreboard objectives add objective dummy
2. Display it in the sidebar: /scoreboard objectives setdisplay sidebar objective
3. Notice how it is visible, though no value has been set yet.
4. Set the display name/number format for a player: /scoreboard players display numberformat a objective styled {}
5. Now, the player a is visible in the sidebar and has a score of 0: /scoreboard players get a objective
6. Try resetting their score with /scoreboard players reset a objective.
7. The score is still here, even after resetting the numberformat: /scoreboard players display numberformat a objective