The Checkstyle trend configuration page do not save all values.

Steps to reproduce:
1)Click on the Configure link below the Checkstyle Trend graph on the Project page.
2)Change the value for width from 500 to 400, and set the # days value to 21
3)Click the save button
4)Click again on the Configure link below the Checkstyle Trend graph on the Project page

Expected:
The width and days field should contain the newly set values.

Actual result:
The width field has the correct value. The days field are empty.