I would not recommend to charge your phone overnight (though it does not practically harm your device):
But the internal heat which is generated when a phone is plugged in, may degrade the battery life slowly over time.
Should Your Phone be Plugged in Overnight? | Digital Trends
Moreover, since you have a S7 Edge (and 'fast charge' feature), you need only max. 1 hour of charging till 80% (this is the sweet spot for Li-ion / Li-po batteries, as per above post & yes, it's true).
Charging a phone overnight is really not required in today's fast paced & "fast charging" world
