#3992 (ok 4.0.8) Multi-row edit doesn't clear values when checking NULL

[IT ArchMerc]

Issue:
When editing multiple rows and checking the NULL checkbox, the current value is not removed (as it is when editing a single row). This prevents the NULL value from being saved and the previous value remains.

Steps to reproduce:
1. Log in to phpMyADmin
2. Select DB
3. Select table
4. Click browse
5. Select multiple rows
6. Click Change
7. Check the NULL checkbox next to a nullable value with a current value set. Notice that the current value is not removed.
8. Click GO at the bottom of the screen
9. Validate the value was not set to NULL

Versions:
phpMyAdmin: 4.0.3deb1.quantal~ppa.2
server: Ubuntu 12.10
PHP: 5.4.6-1ubuntu1.2
MySQL: 5.5.27
Browser: Chrome 27.0.1453.116