Moving through wither roses in Spectator mode and changing game mode after moving away gives the player the wither effect

Related to MC-279016, MC-279021, MC-279031 and MC-279033.

Moving through wither roses while in spectator mode, and then changing the gamemode gives the player the wither effect.

 

Steps to Reproduce:

1. While in spectator mode, fly through a wither rose.
2. Change the player's game mode.

Observed Results:

The player gets the wither effect.

Expected Results:

The player does not take the wither effect as they never touched the wither rose while in creative/survival/adventure.