You will not damage the MAX17220 if voltage is applied at the output and the input is left floating. The MAX17220 has a True Shutdown Mode, which completely disconnects the output from the input and ensures that no reverse current flows from the output to the input. This will prevent the voltage applied at the output from damaging the internal circuitry if the MAX17220. You will want to make sure the EN pin is pulled low to enable True Shutdown Mode.