AFAIK any charger has an over voltage / under voltage protection. So if there is no battery, it wont damage it. The onboard circuits should detect that the battery is missing and give the appropriate message while booting up.
The charger voltage never exceed battery voltage for lithium battery under load condition. Lithium battery can not accept even 5% over voltage. So when charger is connected to laptop / mobile (without battery), due to loading by laptop / mobile, the voltage is maintained at battery level. Hence no damage can be caused.
I am using my laptop, without battery for last 2 years.
Best Regards,
Mukund Deshmukh. Beta Computronics Pvt Ltd 10/1, IT Park, Parsodi, Nagpur-440022 Cell - 9422113746