Steps to reproduce:

1. Create some host and assign any template with HTTP agent items in it.
2. Go to any HTTP agent item on the host level.
3. Check the "Enable trapping", click "Update". Notification says that the item has been updated. Go back to item configuration - "Enable trapping" checkbox will be empty.
4. Repeat step 3, but this time specify some IP in "Allowed hosts" field. There will be the following error - Incorrect value for field "trapper_hosts": should be empty.
   
5. Repeat steps 3 and 4 for the item on the template level - it will be updated successfully and host will inherit the parameters.

Expected:

Parameters must be successfully set on the host level. Latest versions 6.4.11rc1 and 7.0.0beta1 are not affected, only 6.0.26rc1 (and most likely 6.0.25).