Low Description
When a user sets an invalid session timeout (say `30a`) on the session configuration page and presses the Update button, the page correctly marks the fields with the message "The supplied value is invalid.", however it sets the field value to 0 instead back to the valid value that was present before. Zero as a session timeout is itself invalid adding to the not so nice user experience.
To replicate:
1) Install Crowd 2.8.2. and configure it with all the default values
2) Login as admin
3) Go to the Session configuration screen
4) The session timeout should be set to 30
5) Set it to something invalid, e.g. `30a` and press the Update button
6) The page will say that the value was invalid but will also set the value to 0
7) Hit the Update button again
8) The page will respond that 0 is also an invalid value
Expected behaviour:
Instead of setting the value of the session timeout to 0 after the user entered an invalid value into the field, it should be set to the original valid value (the one shown when the page is loaded).