MissingFieldException 'checksName' for Freestyle project

After upgrading JUnit plugin to 1.44 Jenkins warns of unreadable data for freestyle projects that use publish JUnit results.

```
Project type: hudson.model.FreeStyleBuild
Error: MissingFieldException: No field 'checksName' found in class 'hudson.tasks.junit.TestResultAction
```

Since I don't use any custom names I chose to discard the old data. The same day, I upgraded JUnit to 1.45. Unrelated but I mention this just in case, I was finally able to upgrade Jenkins past 2.263 (couldn't due to the div vs tables change).

This morning, the unreadable data messages are shown again. This time, shown using Jenkins 2.269 formatting.

```
Project type:
Error: MissingFieldException: Field not found in class. ---- Debugging information ---- message : Field not found in class. field : hudson.tasks.junit.TestResultAction.checksName
```

I clicked "Discard Unreadable Data". Is this going to continue to happen every day?

Start by reproducing the upgrade path described for Jenkins 2.263-2.269 and JUnit plugin 1.44-1.45, focusing on unreadable Freestyle project data containing hudson.tasks.junit.TestResultAction.checksName. Determine whether the plugin needs compatibility handling for discarded or missing data, then verify that the warning no longer recurs after migration.

Written by the indexing model from the issue text.