When resolving a spell, you follow the instructions of that spell in order as written in the text box. In the case of Sundering Growth, the first thing is to destroy the enchantment. Once that happens, the control changing effect ends immediately (even in the middle of resolving a spell). Then you Populate.
A control-changing effect is not a state-based action or a trigger. It is a continuous effect that is checked all the time. When the effect ends (because the source of the ability leaves the battlefield in this case), the control changes instantaneously to whoever has the most recent control effect (the default is “the player under whose control this originally entered”). So you get your token back in time to populate it!
Today’s Rules Tip written by Nick Rutkowski, Level 2 judge from El Cerrito, CA