PIM-2405 Prevented considering 0 as null for metric data during import

| Q                   | A
| ------------------- | ---
| Bug fix?            | yes
| New feature?        | no
| BC breaks?          | no
| Tests pass?         | yes
| Scenarios pass?     | no
| Checkstyle issues?  |
| Changelog updated?  | yes
| Fixed tickets       | PIM-2406
| Doc PR              |