You can definitely leave your battery connected to a charger overnight with most modern models. While older trickle chargers posed a threat to the integrity and safety of the battery, current models actually feature multiple charging modes that prevent such damage.
A standard charger will come with at least one normal charging mode and a float mode, the latter which will only keep the battery fully charged without overcharging it. With some models, you can leave your battery connected for extended periods of time and ensure you have a full battery ready to go anytime you need it.