correct column name.

refs https://github.com/zikula-modules/Clip/issues/157

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | na
| Fixed tickets | https://github.com/zikula-modules/Clip/issues/157
| Refs tickets  | https://github.com/zikula-modules/Clip/issues/157
| License       | MIT
| Doc PR        |