ADA4941-1 opened input signal

Hello

I am considering Sallen-Key, Low-Pass Filter like figure 54 on the datasheet.

There is a situation that the input is opened.

Then the output would be unstable.

Should I put termination resistor?

If yes, which value can I use?

There is a little oscillation at output because of load capacitance.

How can I compensate it?

Regards,